25th Congress Ampere on Magnetic Resonance and Related Phenomena: Extended Abstracts [1st ed.] 978-3-540-53136-4;978-3-642-76072-3

Table of contents :
Front Matter ....Pages I-XXX
Front Matter ....Pages 1-1
Experiments with an Isolated Subatomic Particle at Rest (Hans Dehmelt)....Pages 2-2
NMR Study of Charge Density Waves (C. Berthier, P. Ségransan, P. Butaud, A. Janossy)....Pages 4-6
NMR Imaging: Current Status and Future Prospects (P. Mansfield, R. J. Coxon, D. N. Guilfoyle, A. M. Blamire, P. Gibbs, P. Harvey et al.)....Pages 7-8
ESR-Experiments on the Two-Dimensional Electron Gas of Heterostructures (K. von Klitzing, M. Dobers, A. Berg)....Pages 9-11
Muon Spin Rotation Experiments in Solids (H. Keller)....Pages 12-13
NMR with Adsorbates on Solid Surfaces (D. Fick)....Pages 14-14
New Approaches in Time-Domain E S R for the Study of Molecular Structures (Arthur Schweiger)....Pages 15-17
Front Matter ....Pages 19-19
ODMR of Defects in Semiconductors (J.-M. Spaeth)....Pages 20-21
14N Endor of the W7 Centre in Natural Type la Brown Diamond (J. M. Baker, M. E. Newton)....Pages 22-23
Time Resolved EPR Studies of Phenazine-TCNQ and Biphenyl-TCNQ Excited Triplets (C. Corvaja, L. Pasimeni, A. Toffoletti)....Pages 24-25
High-Spin Multiplet Endor and Triple Resonance: Its Application to a Model Compound for Organic Ferrimagnets (T. Takui, M. Endoh, S. Kita, Y. Teki, T. Kinoshita, K. Itoh)....Pages 26-27
Local Deformation and Hyperfine Fields on the Ligands in Trigonal Centre Yb3+ in KMgF3 (M. V. Eremin, M. M. Zaripov, I. R. Ibragimov, M. P. Rodionova, M. L. Falin)....Pages 28-29
Spin-Lattice Relaxation of F+—Centers in Neutron Irradiated CaO Crystals (G. Liidja, T. Rõõm)....Pages 30-31
ESR-Investigations on the Solid Solution Mg2-x CuxP4O12 (W. Gunßer, A. Zimmermann)....Pages 32-33
Doping Effect and I (V) Characteristic as Found by E.S.R. (N. Rieux, J. Pescia, Ai Bui, Y. Servant)....Pages 34-35
Optical Detection of Cross-Relaxation of F-Centres and Paramagnetic Impurities in Alkali Halides (P. G. Baranov, V. V. Dyakonov, N. G. Romanov, V. V. Vetrov)....Pages 36-37
Point Defects in Copper Studied by Nuclear Quadrupole Double Resonance using the Field-Cycling Technique (M. Blanz, M. Hampele, G. Majer, M. Notter, A. Seeger)....Pages 38-39
Anharmonic Electron Spin-Lattice Relaxation of the Irradiational Defects in Potassium Selenate and Rochelle Salt Single Crystals (V. A. Ivanshin, I. N. Kurkin, W. Brunner, G. Völkel)....Pages 40-41
The Influence of the Interionic Distance on the Cubic EPR Spectrum of Gd3+ Ion in RBCaF3 Single Crystals (T. Rewaj, M. Krupski, J. Y. Buzaré)....Pages 42-43
EPR of Mn+ Centres in BaF2 and SrF2 (P. G. Baranov, A. Hofstaetter, T. Nickel, A. Scharmann, F. Schön)....Pages 44-45
Light-Induced Changes in the FMR Parameters of CdCr2Se4 (E. Mosiniewicz-Szablewska)....Pages 46-47
Elastical Deformation of Mg2SiO4:Cr3+ (FORSTERITE) and MgO:Mn2+ and Fe3+ by Uniaxial Stress. An in Situ EPR Study (R. Lueck, R. Stoesser, H. Rager, J. Klein, A. Rericha, S. S. Hafner)....Pages 48-49
Antiferromagnetic Resonance in Jahn-Teller KDy(MoO4)2 Type Crystal (M. D. Kaplan)....Pages 50-50
Field Induced Phase Transitions of Ferromagnetic Bilayers with Antiferromagnetic Coupling (W. Schmidt)....Pages 51-52
EPR Investigations of the Dynamics of Doping IONS in Perovskite Lead Titanate Ceramics (W. Windsch, R. Heidler, G. Klotzsche, B. Milsch)....Pages 53-54
Front Matter ....Pages 55-55
Nuclear Spin Relaxation and Atomic Motion in Inorganic Glasses (O. Kanert)....Pages 56-57
A Simple Method Analyzing NMR Line Shape of Mobile Probes in Disordered Solids (E. Rössler, K. Börner, M. Taupitz, H.-M. Vieth, M. Schulz)....Pages 58-59
NMR Determination of Order Parameters in Quadrupolar Glasses (W. Wiotte, S. Elschner, J. Petersson, R. Blinc)....Pages 60-61
Electron Spin Resonance of Vitreous Thioborates (M. Haddad, R. Berger, Y. Servant, A. Levasseur)....Pages 62-63
E.P.R. Study of Disorder and Phase Transitions in Rb1-xKxCaF3 (P. Foucher, J. Y. Buzaré)....Pages 64-65
Spin-Lattice Relaxation in Silicate and Vanadate Glasses (T. Bouhacina, G. Ablart, M. F. Pilod, J. Pescia, Y. Servant)....Pages 66-67
Interpretation of the Asymmetry of NMR Spectral Lines in Amorphous Materials (I. Pócsik)....Pages 68-69
New Interpretation of Diffusion and Relaxation Processes in Amorphous Materials (I. Pócsik)....Pages 70-71
Cluster Selective Relaxation Behaviour in the Deuteron Glass Rb0.56(ND4)0.44D2PO4 (N. Korner, J. Dolinsek, R. Kind)....Pages 72-73
Two-Dimensional NMR Separation of Inhomogeneous vs. Homogeneous Lineshapes in the Glassy State: 87Rb in Proton Glass Dradp (J. Dolinšek)....Pages 74-75
Solid State NMR Spectra of Microporous Aluminophosphates (P. J. Grobet, H. Geerts, J. A. Martens, P. A. Jacobs)....Pages 76-77
Ferroelastic Domain Structure in Incommensurate Phase in Trigonal Double Molybdates and Tungstates (W. Zapart, M. B. Zapart)....Pages 78-79
Nonexponential 2H-NMR Spin-Lattice Relaxation as a Signature of the Glassy State (W. Schnauss, F. Fujara, K. Hartmann, H. Sillescu)....Pages 80-81
The Partial Crystallization Effect on the EPR Spectra from Bi-Sr-Ca-Gd-Cu-O Vitreous Matrices (S. Simon, O. Cozar, I. Barbur, V. Simon, I. Ardelean, Gh. Ilonca et al.)....Pages 82-83
The Valence States and Interaction between Chromium Ions in Lithium-Borate Glasses (O. Cozar, I. Ardelean, Gh. Ilonca, S. Simon, I. Barbur, I. Bratu)....Pages 84-85
Results of high-field 31P-NMR investigations of crystalline and amorphous phosphate systems with increased spectral resolution (B. Schnabel, P. Hartmann, P. Losso)....Pages 86-86
Front Matter ....Pages 87-87
Nuclear Magnetic Resonance Microscopy Principles, Limits and Applications (Winfried Kuhn)....Pages 88-89
NMR Imaging of Solids with Magic Angle Spinning (W. S. Veeman, G. Bijl)....Pages 90-91
Stray-Field Imaging of Solids (STRAFI) (A. A. Samoilenko, K. Zick)....Pages 92-93
Detection of Chemical Waves by Magnetic Resonance Imaging (R. L. Armstrong, A. Tzalmona, M. Menzinger, A. Cross, C. Lemaire)....Pages 94-95
Nondestructive Evaluation of Polymer Compounds by Solid State NMR Imaging (P. Blümler, E. Günther, G. Schauss, H. W. Spiess, B. Blümich)....Pages 96-97
NQR Imaging (E. Rommel, P. Nickel, R. Kimmich, D. Pusiol)....Pages 98-99
Imaging of Solids by Audio Frequency Excitation in the Rotating Frame (F. De Luca, B. C. De Simone, P. Fattibene, N. Lugeri, B. Maraviglia)....Pages 100-100
NMR Microscopy of Plant Systems at 11.7T (R. Bowtell, G. Brown, P. Glover, M. McJury, P. Mansfield)....Pages 101-102
EPR Imaging Applications in Solid Polymers (J. Dahm, V. Macho, G. G. Maresch, D. Davidov, H. W. Spiess)....Pages 103-104
NMR Imaging and Volume-Selective Spectroscopy in Solids: Product Operator Formalism and Test Experiments (S. Hafner, E. Rommel, R. Kimmich)....Pages 105-106
Response to Tip-Angle and Spin-Lock RF Pulse Sequences in the Presence of Magnetic Field Gradients: Slice-Selective Excitation in NMR Imaging Experiments (D. E. Demco, F. Balibanu, R. Kimmich)....Pages 107-108
On the Proton T2 Effects of Oxygen-17 as an NMR and MRI Label for Water in Living Systems (A. L. Hopkins, E. M. Haacke, W. D. Lust, P. A. Wielopolski, R. G. Barr, C. B. Bratton)....Pages 109-110
Double Resonance Rare Nuclei Imaging (F. De Luca, R. Campanella, A. Bifone, B. Maraviglia)....Pages 111-111
Perspectives of the Use of Magnetically Labeled Antibodies in NMR Imaging (M. A. Macri, F. De Luca, G. Garreffa, B. Maraviglia)....Pages 112-112
Imaging of 7LI in a Polymer Electrolyte Film PEO8 (LiCIO4): A Preliminary Investigation (M. Sonderegger, J. Roos, M. Mali, D. Brinkmann)....Pages 113-114
Spatially Resolved T1 Relaxation Measurements of Brine in Rock Cores (J. J. Attard, T. A. Carpenter, L. D. Hall, P. A. Osment, K. J. Packer, M. J. Taylor)....Pages 115-115
Localized NMR Spectroscopy with a 1.5 T Whole Body Imager (W.-I. Jung, O. Lutz, K. Müller, M. Pfeffer, M. Rieckert, F. Schick)....Pages 116-116
Front Matter ....Pages 117-117
Creation, Migration and Observation of Longitudinal Multiple-Spin Order (Geoffrey Bodenhausen)....Pages 118-119
Quadrupolar Echoes on Spin I> 1 Nuclei (I. Furó, B. Halle)....Pages 120-120
NMR Studies of Double Proton and Deuteron Transfers in Liquids and Solids (H. H. Limbach, H. Rumpel, B. Wehrle, L. Meschede, M. Schlabach, G. Scherer et al.)....Pages 121-122
Transfer of Spin Order in Solids. Deterministic and Diffusive Behavior (G. Aebli, B. H. Meier, R. R. Ernst)....Pages 123-123
Multiple Spin Echoes in a Liquid in a High Magnetic Field (R. Bowtell, R. M. Bowley, P. Glover, A. Bedford)....Pages 124-125
NMR Line Shape in Solids (E. I. Fedin)....Pages 126-126
ESR Lineshape for Exchanging Anisotropic Spin Systems (N. P. Benetis, R. Erickson, Lars Sjöqvist, A. Lund, J. Maruani)....Pages 127-128
Cross Polarization to Low-γ Nuclei (A. Sebald, L. H. Merwin)....Pages 129-129
High-Resolution Solid-State NMR Spectroscopy of Heavy Spin-1/2 Nuclei: Interactions with Neighboured Quadrupolar Nuclei (A. Sebald, A. Grimmer)....Pages 130-130
Phonon Contribution to the AFMR Linewidth of a Heisenberg Antiferromagnet (T. J. Drye, J. W. Tucker)....Pages 131-132
EPR of Solitons in One-Dimensional Antiferromagnets (J. Kuriata, L. Sadłowski, B. Bojanowski, M. Wabia, M. L. Falin, V. V. Izotov)....Pages 133-134
ESR Pumping of Atomic Hydrogen Gas at Low Temperature (A. Ya. Katunin, S. A. Vasilvev, I. I. Lukashevich, E. Tjukanov, S. Jaakkola)....Pages 135-135
Multiple Spin Echo Signals in Systems with Mutual Guadrupole (T. Sh. Abesadze, R. A. El-egaimi)....Pages 136-137
Nuclear Spin Echo Amplification in Magnetics, Caused by Resonator Effects (N. P. Fokina, K. O. Khutsishvili)....Pages 138-139
Orientation Selective ESEEM of Nitrogen Coordinated Oxo-Vanadium(IV) Complexes (E. J. Reijerse, D. Collison)....Pages 140-141
Memory Effects in the Problems of Magnetic Resonance and Magnetic Relaxation (R. R. Nigmatullin, D. A. Tayurskii)....Pages 142-143
Cross-Relaxation in Paramagnetic Crystals at Low Temperatures (D. A. Tayurskii)....Pages 144-145
Multiple-Quantum NMR Spectroscopy of Half-Integer Quadrupolar Nuclei in Rotating Solids (N. C. Nielsen, H. Bildsøe, H. J. Jakobsen)....Pages 146-147
Dihydrogen Addition Studies by the Pasadena Effect (C. R. Bowers, P. J. Carson, D. J. Norris, D. P. Weitekamp)....Pages 148-149
On Threshold of Parametric Instability of Spin Waves in a Film with Rough Surface (V. B. Cherepanov)....Pages 150-150
Spin-Wave Theory of NMR in Solids at Low Temperatures (E. B. Feldman, A. K. Khitrin)....Pages 151-152
Propagation and Trapping of Phonons in Solids with Resonant Paramagnetic Centers (B. I. Kochelaev, A. E. Solovyev, D. V. Chystyakov)....Pages 153-154
Front Matter ....Pages 155-155
A Magnetic View of the Reaction Center (James R. Norris, Theodore J. DiMagno, Mala Raghavan, Ranjan Das)....Pages 156-157
Magnetic Resonance of the Triplet State of Carotenoids in Photosynthesis (A. Angerhofer, V. Aust)....Pages 158-159
Electron Spin Echo Studies of Nonradiative Molecular Triplet States (E. J. J. Groenen)....Pages 160-161
A Novel Radical-Triplet Pair Mechanism for Cidep of Free Radicals (C. Blättler, F. Jent, H. Paul)....Pages 162-163
Time Resolved ESR Studies of Photoinduced Spin Correlated Radical Pairs in Photosynthetic Reaction Centres (A. J. van der Est, C. H. Bock, I. Sieckmann, D. Stehlik)....Pages 164-165
Dipolar relaxation enhancement in inhomogeneous systems. Application to the oxygen evolving complex of plant photosynthesis. (R. G. Evelo, A. J. Hoff)....Pages 166-166
Transient EPR of Spin Polarized Triplet States and Correlated Radical Pairs in Viscous Liquid Crystals (R. Bittl, N. Rösch, S. Weber, A. Münzenmaier, G. Kothe)....Pages 167-168
Magnetic Resonance and Photochemistry: The Red-Photolysis of Solid Humulene Nitrosite (Z. F. Khan, D. K. MacAlpine, A. L. Porte, J. E. Schubert, G. A. Sim)....Pages 169-170
Novel Coupling Mechanism in Spin-Wave Instabilities (G. Wiese, H. Benner)....Pages 171-172
ODMR Studies of Protein-Nucleic Acid Interactions (D. H. H. Tsao, A. H. Maki)....Pages 173-174
Endor-Studies of P865+· in Reaction Center Single Crystals of Rb. sphaeroides R-26 at 8° C (F. Lendzian, B. Endeward, M. Plato, K. Möbius, W. Lubitz)....Pages 175-176
RYDMR in Reaction Centers of Photosynthetic Bacteria (E. Lang, W. Lersch, R. Feick, W. J. Coleman, D. C. Youvan, M. E. Michel-Beyerle)....Pages 177-178
Front Matter ....Pages 179-179
Optical Spin Polarization and Spin Waves in Helium Three Gas (G. Vermeulen, F. Laloë)....Pages 180-181
Chemical Exchange and Quantum Exchange (Narayanan D. Kurur, Daniel H. Jones, Daniel P. Weitekamp)....Pages 182-183
Stimulated Nuclear Polarization. (E. G. Bagryanskaya, I. V. Koptuyg, R. Z. Sagdeev)....Pages 184-185
DNP and ESR at 5 T Fields (T. F. Prisner, S. Un, R. T. Weber, A. C. McDermott, D. J. Singel, R. G. Griffin)....Pages 186-187
Weak Field Dynamic Nuclear Polarization with Phosphorus Radicals. (Y. Ayant, N. Kernevez, L. Secourgeon, P. Tordo)....Pages 188-189
NMR-Investigations of Homogeneous Hydrogenation Reactions using Para Hydrogen (J. Bargon, J. Kandels, P. Kating, A. Thomas, K. Woelk)....Pages 190-191
Odendor of F-Centres without Microwaves and Thallium Impurity NMR in Kcl:Tl Detected with the MCDA Technique (N. G. Romanov, D. M. Hofman, J. M. Spaeth)....Pages 192-193
31P Relaxation Mechanisms in Phosphorus Metabolites (E. R. Andrew, W. S. Brey, R. Gaspar Jr.)....Pages 194-195
Dynamic Study of Glassy Properties of Deuteron Glass Rb1-x(ND4)x D2 PO4 Using31P NMR Spin-Lattice Relaxation (S. Chen, D. C. Ailion)....Pages 196-197
Magnetic Resonance of Probe Yb3+ and Er3+ Ions in the Antiferromagnetic Phase of DyPO4 (J. M. Baker, B. Bleaney, A. A. Jenkins, P. M. Martineau)....Pages 198-199
Contribution of Hydrogen Bonding (HB) to the Leakage Factor in Dynamic Nuclear Polarization (DNP) (M. P. Ferroud-Plattet, N. Kernevez, Y. Ayant, A. Salvi)....Pages 200-201
19F-Spin-Lattice Relaxation of PF6- Intercalated in Graphite (I. Stang, M. Kraus, K. Lüders)....Pages 202-203
Cu NQR and Li NMR Relaxation in the Paramagnetic Phases of CuO and CuO:Li (A. Lascialfari, S. Aldrovandi, M. Fanciulli, F. Borsa, M. Corti, A. Rigamonti)....Pages 204-205
Spin-Lattice Relaxation of Three-Spin System through Intermolecular Dipole-Dipole Interaction (G. Ślósarek)....Pages 206-206
AB Initio Calculations of Zero-Field Splitting in Nickel(II) Complexes: Implications for Electron and Nuclear Spin Relaxation (Jozef Kowalewski, Michael Odelius, Carl Ribbing)....Pages 207-207
Extremely Narrow Lines in the ESR Spectra at Longitudinal Double Modulation of a Magnetic Field (B. F. Alekseev, Ju. V. Bogachev, A. B. Tikhonov)....Pages 208-209
Lanthanide (III) Ions Coordination and Water Mobility in Aqueous Solutions: Solvent Nuclear Magnetic Relaxation Study (V. I. Chizhik, A. V. Rushai, V. V. Matveev, N. R. Skrynnikov)....Pages 210-211
The Influence of Hydrolysis on the Quadrupole Relaxation of Monoatomic Ion Nuclei in the Electrolyte Solutions (V. I. Chizhik, V. I. Mikhailov, E. Ylinen, A. Vuorimäki)....Pages 212-213
Computer Simulation of Spin Relaxation in Diluted Lattices (Sushil K. Misra, Ufuk Orhun)....Pages 214-214
Inhomogeneous Dipolar Broadening and Hyperfine Shifts of Protons Resonance Lines in Solution with Paramagnetic Impurities (E. Belorizky, P. Fries, W. Gorecki, M. Jeannin, P. Maldivi, E. Gout)....Pages 215-216
Spin-Lattice Relaxation of 7Li in Hexagonal and Cubic LixTiS2 (W. Küchler, P. Heitjans, D. Clausen, A. Payer, R. Schöllhorn)....Pages 217-218
2H and 13C NMR Investigations of Fluorene Single Crystals with Optical Nuclear Polarization (G. Buntkowsky, W. Hoffmann, H. M. Vieth)....Pages 219-219
Fast Electron Transfer Kinetics in Photosystem I from Transient EPR-Spectrosoopy at Room Temperature (I. Sieckmann, C. Bock, K. Brettel, A. van der Est, P. Sétif, D. Stehlik)....Pages 220-221
High Field Nuclear Spin Relaxation in Liquids and Solids (G. Diezemann, W. Schirmacher)....Pages 222-222
Nuclear Ferromagnetism in KMgF3 (P. Bonamour, V. Bouffard, C. Fermon, M. Goldman, J.-F. Jacquinot)....Pages 223-224
Chlorine Quadrupole Relaxation in SnCl2. 1.5 H2O (J. Pirnat, J. Lužnik, Z. Trontelj)....Pages 225-226
Numerical Narrowing of EPR Spectra by Differentiation with Smoothing (Andrzej B. Wieckowski)....Pages 227-229
Front Matter ....Pages 229-229
A Correlation of the Spin-Lattice Relaxation with the Starch Content in the Grains of a Cereal (R. Degli Agosti, R. Lenk, H. Greppin)....Pages 230-231
Surface Adsorbed Free Radicals Observed by Positive Muon Avoided Level Crossing Resonance (Emil Roduner, Ivan D. Reid)....Pages 232-233
The ESR and ENDOR of Catalytically Active Ti Complexes (Ju Azarny, Ju Bogachev, S. Booder, V. Volodenko, V. Drapkin, A. Serdyuk et al.)....Pages 234-235
The ESR of Deuterium in Water: The Practical Aspects of the Problem (A. Grushkin, V. Drapkin, A. Serdyuk, N. Serebrennikova)....Pages 236-237
29Si Solid-State NMR Study of the Hydration Products of Tricalcium Silicate in Pastes and Diluted Aqueous Suspensions (R. Rassem, H. Zanni-Théveneau, P. Barret, A. Nonat, D. Bertrandie)....Pages 238-239
The Possibility of Laser Generation in Ferromagnets with Dynamic Frequency Shift (K. O. Khutsishvili, S. G. Chkhaidze)....Pages 240-241
Front Matter ....Pages 243-243
NMR Study of Highly Correlated Superconductivity (Y. Kitaoka)....Pages 244-245
NMR Spin-Lattice Relaxation and EPR Linewidth in High Tc Materials (S. Chakravarty, R. Orbach)....Pages 246-247
Microwave Absorption of Superconductors at Low Magnetic Fields (K. W. Blazey)....Pages 248-248
Measurement of Surface Magnetic Field of Superconductor by Magnetic Resonance (Y. Maniwa, H. Sato, T. Mituhashi, K. Mizoguchi, I. Shiozaki, A. Shinogi et al.)....Pages 249-250
Proton Relaxation in the Superconducting Organic Solid (BEDT-TTF)2Cu(NCS)2: Evidence for Relaxation by Localized Paramagnetic Centers (T. Klutz, U. Haeberlen, D. Schweitzer)....Pages 251-252
NQR Study of CU in YBa2Cu3O6.95 (M. Kieninger, G. Majer, A. Seeger)....Pages 253-254
Magnetic Resonance below Tc in the Oxygen-Deficient Rba2Cu3OX Superconductors (A. G. Badalyan, P. G. Baranov)....Pages 255-256
Spin-Lattice Relaxation, NQR 63Cu and NMR 205Tl, 17O in Tl2Ba2CanCun+1O6+2n (n=0,1,2) (S. V. Verkhovskii, Yu. I. Zhdanov, K. N. Mikhalev, B. A. Aleksashin, V. I. Ozhogin, A. Yu. Yakubovskii et al.)....Pages 257-258
Magnetization Relaxation in HTSC as Studied by Microwave Response (G. G. Lazarev, D. S. Tipikin, Ya. S. Lebedev)....Pages 259-260
Cu NQR-Echo in Superconducting YBa2Cu3O7-x in Weak External Magnetic Field (H. Schmiedel, S. Grande, G. Mayer, B. Lippold)....Pages 261-262
On the Influence of Oxygen Deficiency upon EPR Spectra of TmBa2Cu3O7-δ (N. Guskos, Ch. Trikalinos, S. M. Paraskevas, A. Koufoudakis, C. Mitras, H. Gemari-Seale et al.)....Pages 263-264
A Microwave Study of Ceramic High-TC Superconductors (I. Ciccarello, M. Guccione, M. Vigni)....Pages 265-266
NMR Investigation of Oxygen-17 in the Bi-Sr-Ca-Cu-O High-TC Superconductors (A. Trokiner, L. Le Noc, R. Mellet, D. Morin, Y. M. Gao, J. Primot et al.)....Pages 267-268
Theory of Nuclear Magnetic Relaxation in HTSCs (A. Yu Zavidonov, M. V. Eremin)....Pages 269-270
63Cu Nuclear Magnetic Relaxation in YBaCuo (O. N. Bakharev, A. V. Egorov, V. V. Naletov, M. S. Tagirov, M. A. Teplov)....Pages 271-272
Microwave Absorption near Tc in a Superconducting Al-Oxide Triangular Sierpinski Carpet (B. Senning, J. E. Drumheller, P. Erhart, L. Fransioli, P. Martinoli, R. Meyer et al.)....Pages 273-274
Decay of Microwave Absorption Signal in High-Tc Superconductors of YBa2Cu3Ox (P. Erhart, J. E. Drumheller, B. Senning, S. Mini, L. Fransioli, E. Kaldis et al.)....Pages 275-276
La NQR and Relaxation Study of La2Cu1-xNixO4 (T. Rega, J. Choisnet, F. Borsa, M. Corti, A. Rigamonti)....Pages 277-278
17O NMR in Oxides and Oxide-Based Ceramics (T. J. Bastow, S. N. Stuart)....Pages 279-279
Probing Y-Ba-Cu-O Superconductors by Temperature and Pressure Dependent NQR Frequencies (I. Mangelschots, H. Zimmermann, H. P. Meister, M. Mali, J. Roos, D. Brinkmann et al.)....Pages 280-281
Static and Dynamic Electronic Susceptibilities in the YBa2Cu4O8 Superconductor from Knight Shift and Relaxation Measurements (H. Zimmermann, I. Mangelschots, M. Mali, J. Roos, D. Brinkmann, E. Kaldis et al.)....Pages 282-283
Magnetic Properties Investigated by EPR and Static Susceptibility in the Superconducting System Y1-xGdxBa2Cu3O7-δ (Al. Nicula, A. V. Pop, L. V. Giurgiu, Al. Darabont, I. Cosma)....Pages 284-285
EPR Study of Spin Dynamics of Kondo Systems (N. G. Fazleyev, G. I. Mironov)....Pages 286-287
NMR Studies of Dilute Magnetic Alloys and Superconductors (N. G. Fazleyev, G. I. Mironov)....Pages 288-289
Multipolar Interaction Effects in Magnetic Resonance Studies of Conductors and Superconductors (N. G. Fazleyev)....Pages 290-291
NMR of Rare Isotope 43Ca in HTSC Tl2Ba2CaCu2O8 (A. Yu. Yakubovskii, V. I. Ozhogin, L. D. Shustov, V. P. Tarasov, V. I. Privalov, G. A. Kirakosjan et al.)....Pages 292-292
Cu NQR and NMR Relaxation in La2-xSrxCuO4 (M. Corti, F. Borsa, A. Rigamonti)....Pages 293-294
Charge Fluctuations and Superconductivity of Highly Correlated Electrons (A. N. Kocharian, P. S. Ovnanian)....Pages 295-296
17O, 63Cu and 89Y NMR Investigation of Spin Fluctuations in High TC Superconducting YBa2Cu3O6+x (C. Berthier, Y. Berthier, P. Butaud, M. Horvatić, P. Ségransan)....Pages 297-298
Nuclear Spin Relaxation in (BEDT-TTF)-Based Organic Superconductors (V. Skripov, A. P. Stepanov)....Pages 299-300
EPR Detection of the Magnetic Structure in High-Tc Superconductors (A. Dulcic, B. Rakvin, M. Pozek)....Pages 301-302
Front Matter ....Pages 303-303
Planar Diffusion, Discrete Jumps and Restricted Diffusion in Columnar Mesophases (Z. Luz, R. Poupko, S. Zamir, S. Alexander, H. Zimmermann)....Pages 304-305
The Rheo-NMR Approach to the Viscoelastic Properties of Liquid Crystalline Polymers: Main-Chain versus Side-Chain Results (Assis F. Martins)....Pages 306-307
Nematic Configuration in Submicron Cylindrical Cavities: 2H NMR Study (G. Crawford, M. Vilfan, I. Vilfan, J. W. Doane)....Pages 308-309
Theory of Dipolar Relaxation in Lamellar System : Application to Lyotropic Mesophases (J.-P. Korb, Th. Bredel, C. Chachaty, J. R. C. Van der Maarel)....Pages 310-311
Supercon Fringe-Field NMR Investigation of Diffusion in Molecular Length Scales: Linear Polymers, Networks, and Percolating Clusters of Biopolymer Hydration Shells (W. Unrath, F. Klammler, K. Kotitschke, R. Kimmich, E. Rommel)....Pages 312-313
Diffusion Measurements in Chiral Liquid Crystals (R. Stannarius, H. Schmiedel)....Pages 314-314
CP/MAS NMR Study On Hydrogen-Bonding Interaction and Morphology of Poly (Vinyl Alcohol)-Poly (Acrylic Acid) Blends and Poly (Vinyl Alcohol)-Poly (Methacrylic Acid) Complexes Systems (Xiaoqing Zhang, K. Takegoshi, K. Hikichi)....Pages 315-316
Polymorphic Crystal Structure of Poly(P-Phenylene Sulphide) by 1H NMR Method (J. Jurga, J. Kubis, P. Hruszka)....Pages 317-318
2D-Deuteron NMR Studies of Ultraslow Motions in Solid Polymers Phenylflips in the Glassy State and Chain Motions at the Glass Transition (D. Schaefer, M. Hansen, B. Blümich, H. W. Spiess)....Pages 319-320
Identification of a Defect Chain Motion in n-Alkanes by Means of NMR Spin-Lattice Relaxation Time Measurements (E C Reynhardt, I Basson)....Pages 321-322
Collective Order Fluctuations in Liquid Crystals Studied by Transverse Nuclear Spin Relaxation (J. Stohrer, G. Gröbner, C. Mayer, K. Weisz, G. Kothe)....Pages 323-324
Fractal Structure of a Cross-Linked Polymer Resin.A Pulsed Field Gradient, Paramagnetic Relaxation and Small Angle X-Ray Scattering Study (C. Chachaty, J.-P. Korb, J. R. C. Van der Maarel)....Pages 325-326
3D 13C MAS NMR Experiment Correlating Order and Dynamics (Y. Yang, A. Hagemeyer, K. Zemke, H. W. Spiess)....Pages 327-328
EPR Study of Free Radicals in Liquid Crystalline Polymers (F. Szöcs, M. Klimová, Z. Hloušková, J. Plaček)....Pages 329-330
NMR Study of the Polymer Solid Electrolyte PEO (LIBF4)x (J. P. Donoso, M. G. Cavalcante, W. Gorecki, C. Berthier, M. Armand)....Pages 331-332
Structure and Dynamics of Discotic Liquid Crystal Polymers (W. Kranig, J. Hirschinger, C. Boeffel, H. W. Spiess)....Pages 333-334
Effect of Translational Diffusion on NMR Spectra of Confined Liquid Crystals (S. Kralj, M. Vilfan, S. Žumer)....Pages 335-336
Rotational Viscosity in a Re-entrant Liquid Crystal Mixture — a NMR Study (A. S. Sailaja, B. Jagadeesh, K. Venu, V. S. S. Sastry)....Pages 337-338
Molecular Dynamics in 40.9 — Proton Spin Relaxation Study (G. Ravindranath, K. Venu, V. S. S. Sastry)....Pages 339-340
Molecular Orientation Time of Liquid Crystals in Low Magnetic Field (C. M. Whittaker, S. L. Segel, D. T. Amm)....Pages 341-342
Solid State13C NMR Study of Macroporous Glycidyl Methacrylate-Ethylene Dimethacrylate Copolymers and of their Derivatives (J. Spěváček, J. Straka, B. Schneider)....Pages 343-344
A Simplified Technique for Analysing Dipolar Couplings of Molecules Oriented in Liquid Crystals (Juhani Lounila, Mika Ala-Korpela, Jukka Jokisaari)....Pages 345-346
NMR1H-NQR14N Cross-Relaxation Spectra in Nematic Ebba (S. V. Dvinskih, Yu V. Molchanov, D. V. Prokopjev)....Pages 347-347
NMR of Oriented Flexible Molecules (C. Schmidt, M. E. Rosen, S. P. Rucker, D. Caplan, M. F. Quinton, A. Pines)....Pages 348-349
2H-NMR Studies on Uniaxially Drawn UHMW-Polyethylene (H. Deckmann, M. Kunz, M. Möller, P. J. Lemstra, C. W. M. Bastiaansen)....Pages 350-350
High-Resolution Solid-State 13C NMR Study on Effects of Blending on Chain Dynamics in Polystyrene/Poly (Vinyl Methyl Ether) Blends (K. Takegoshi, Kunio Hikichi)....Pages 351-351
Quadrupole Couplings of 83Kr and 131Xe in Liquid-Crystalline Environments (L. P. Ingman, J. Jokisaari, P. Diehl)....Pages 352-353
ESR and Endor Studies of Unusually Stable Trapped Electrons in Brominated Epoxy Polymer Resins Exposed to UV-Irradiation (J. Kobayashi, J. Enomoto, T. Takui, K. Itoh)....Pages 354-355
D-NMR Study of Microscopic Effects in Collapsing Pa Gels (M. Corti, L. Pavesi, A. Rigamonti, F. Tabak)....Pages 356-357
High Pressure Influence on Processes of Free Radical Stabilization in Irradiated Polymethylmethacrylate Copolymers (S. P. Pivovarov, L. A. Vasilevskaya, A. Bakhtigereyeva)....Pages 358-358
EPR and ENDOR Study of Semiquinones in Reversed Micelles (D. Niethammer, B. Kirste, H. Kurreck)....Pages 359-360
Chain Dynamics of a Liquid Crystal Studied by Proton N.M.R. Relaxation Dispersion (P. J. Sebastião, A. C. Ribeiro, A. F. Martins, A. M. Giroud-Godquin, F. Noack)....Pages 361-361
Proton Relaxation in a Fractal Polymer Chain (A. Zidanšek, R. Blinc, G. Lahajnar, V. Žagar, A. Blinc)....Pages 362-363
Hydrogen Bonds and Formation of Dimers in Some Liquid Crystals (A. Zheliaskova, I. Zupancic, G. Lahajnar, A. Derzhanski)....Pages 364-365
NMR Study of a Ferroelectric Liquid Crystal with Polarization Sign Reversal (M. Luzar, J. Dolinšek, R. Blinc)....Pages 366-367
A Model for Correlated Internal Motions and Deuteron Spin Relaxation in Liquid Crystals (Ronald Y. Dong)....Pages 368-368
NMR Studies of Dynamics in Molecular Crystals (Stephen J. Heyes, Christopher M. Dobson)....Pages 369-369
Frequency Dependent Selective Relaxation Studies of Deuterons in Liquid Crystals (K. H. Schweikert, H. Gotzig, F. Noack)....Pages 370-371
Front Matter ....Pages 373-373
Multistability and Chaos in Transverse-Pumped Spin-Wave Instabilities (H. Benner, F. Rödelsperger, G. Wiese)....Pages 374-375
Hyperchaos in Antiferromagnetic Resonance (H. R. Moser, P. F. Meier, M. Warden, F. Waldner)....Pages 376-377
Critical spin fluctuations and Curie temperatures of ultrathin Ni films on W(110): A magnetic-resonance study in UHV (Yi Li, M. Farle, K. Baberschke)....Pages 378-379
Phase Transitions in Acceptor-Graphite Intercalation Compounds: An ESR Study (C. Rettori, S. Rolla, A. M. Gennaro, G. E. Barberis)....Pages 380-382
NMR Lineshapes and Relaxation in Incommensurate Systems with Four and Six Components Order Parameters (R. Blinc, S. Žumer)....Pages 383-384
Local and Non-Local Probes in NMR-NQR (R. Kind, O. Liechti)....Pages 385-386
NMR/NQR Studies of Phase-Transition Precursors (John L. Bjorkstam)....Pages 387-388
14N-NMR study of the normal, incommensurate and commensurate phases of (NH4) 2ZnCl4 (D. Michel, B. Müller, J. Petersson, A. Trampert, R. Walisch)....Pages 389-390
Fractal Dimensions and Lyapunov Exponents of NMR-Laser Attractors (L. Flepp, R. Holzner, E. Brun, Ch. Broens)....Pages 391-391
Noise and Coherence in NMR-Laser Dynamics (L. Flepp, R. Holzner, E. Brun, H. R. Moser)....Pages 392-393
NMR-Laser Dynamics Near a Hopf Bifurcation (R. Holzner, A. W. McCord)....Pages 394-395
EPR Evidence for an Intermediate Premartensitic Transition in Pb3(PO4)2 (I. Barbur, S. Simon, I. Ardelean, Gh. Cristea)....Pages 396-397
Coupling of Rotational Motions at Phase Transitions in Tetrabutylammonium Tetrafluoroborate (C4H9)4 N BF4 (B. Szafrańska, A. Kozak, Z. Pająk)....Pages 398-399
Proton NMR Study of the Structural Phase Transitions in Bilayer N-Alkylammonium Chlorides: C9H19ND3Cl and C11H23ND3Cl (S. Jurga, A. Woźniak, C. Boeffel)....Pages 400-401
EPR Study of the Phase Fluctuation Near T1 in the Incommensurate [Mg(H2O)6]SiF6 (R. Hrabański)....Pages 402-403
Critical Exponent in Normal to Incommensurate Phase Transition in KSc(MoO4) by EPR (W. Zapart)....Pages 404-405
39K and 2H NMR Investigation of the Antiferroelectric Transition in KOH and KOD (T. J. Bastow, S. L. Segel, K. R. Jeffrey)....Pages 406-406
87Rb NMR Study of the Glassy Transition in Rb0.68(ND4)0.32D2AsO4 (B. Zalar, J. Dolinšek, R. Blinc)....Pages 407-408
NMR Study of Martensitic Transformation in Shape Memory Alloys (S. Rubini, C. Dimitropoulos, R. Gotthardt)....Pages 409-410
Study on the Structural Phase Transition in 1, 2, 4, 5-Tetrachlorobenzene (Carlos A. Martín)....Pages 411-412
Front Matter ....Pages 413-413
Thermally Detected Electron Spin Resonance of Fe2+ in LiNbO3 (S. Juppe, O. F. Schirmer)....Pages 414-415
Longitudinally Detected Pulsed ESR Spectroscopy: Low Power Experiments (A. Colligiani, M. Lucchesi, M. Martinelli)....Pages 416-417
Frequency Modulated Oscillators with Soluble Dynamics: A Model for Resonance Spectroscopy (E. van Faassen)....Pages 418-419
Progressive Saturation Relaxation Spectroscopy Method for NMR Investigation of Biological Tissues and Condensed Matter (I. Pócsik, P. Rácz)....Pages 420-421
Bistability and Stochastic Resonance in Electron Paramagnetic Resonance (L. Gammaitoni, S. Santucci, M. Giordano, M. Martinelli, L. Pardi)....Pages 422-423
Recent Developments on the Pulsed Field Gradient NMR Technique for Self Diffusion Coefficient Measurements on Various Nuclei (Th. Dippel, K. D. Kreuer, M. Hampele, A. Rabenau)....Pages 424-425
1D and 2D Solid State NMR of Homonuclear Systems using Magic Angle Spinning (James C. Duchamp, Xiaoling Wu, Kurt W. Zilm)....Pages 426-427
Application of an Inverse Laplace Transform Method to Analysis of Decaying Transients (Yves Balcou)....Pages 428-429
Quadrupolar Echo Train Relaxation of Spin S = 3/2 Nuclei (J. R. C. van der Maarel)....Pages 430-431
Applicability of the LPSVD Technique for the Analysis of High-Resolution Solid-State Carbon-13 NMR Spectra of Complex Organic Solids (D. Michel, F. Engelke, W. Kölbel)....Pages 432-433
NMR Parameter Estimation by Proper Model Order Selection (S. Kang, D. Fiat)....Pages 434-435
Magic Angle Spinning NMR Investigations of Molecular Motions and Spin Dynamics in 1-Cyanoadamantane (F. Engelke, J. Petersson, P. Simon)....Pages 436-437
Experimental Aspects of 17O Solid-State NMR Spectroscopy (Roman Goc, Daniel Fiat)....Pages 438-439
Investigation by the Methods of NMR and Angular Correlation of Annihilation Photons (ACAP) of Cyclotron Irradiated Copper (R. K. Zhakparov, A. I. Kozin, S. V. Makarov, S. P. Pivovarov)....Pages 440-440
A Pulsed ENDOR Probehead with an Operating Frequency Range Up to 200 MHz (Jörg Forrer, Susanne Pfenninger, Josef Eisenegger, Arthur Schweiger)....Pages 441-442
Radio Frequency Driven Electron Spin Echo Envelope Modulation (Susanne Pfenninger, Herman Cho, Jörg Forrer, Arthur Schweiger)....Pages 443-444
Creation and Detection of Nuclear Spin Coherence using Novel Electron Spin Echo Pulse Sequences (E. J. Hustedt, C. Gemperle, A. Schweiger, R. R. Ernst)....Pages 445-446
Two New Pulsed EPR Experiments: FT — EPR Detected NMR and FT — Hyperfine — Spectroscopy (Thomas Wacker, Arthur Schweiger, Richard R. Ernst)....Pages 447-448
Gaussian Pulse Cascades and Selective Two-Dimensional NMR (Lyndon Emsley, Peter Huber, Lorenzo Di Bari, Josef Kowalewski, Geoffrey Bodenhausen)....Pages 449-450
Wide-Band NMR Spectroscopy with Frequency-Modulated “Chirp” Pulses (Jean-Marc Böhlen, Irene Burghardt, Robert Konrat, Martial Rey, Geoffrey Bodenhausen)....Pages 451-451
Nuclear Quadrupol Resonance Spectrometer (V. Ioncu, Gh. Cristea, I. Barbur, E. Tataru, S. Simon)....Pages 452-453
Deadtime Free Echo Modulation in Pulsed EPR (A. Grupp, Z. Shanmin, M. Mehring)....Pages 454-455
A Fast Field—Cycling N.M.R. Spectrometer (M. Blanz, T. J. Rayner, J. A. S. Smith)....Pages 456-457
Design and Construction of a 2.4 T Air-Cored Copper Magnet for Fast Field-Cycling NMR (St. Becker, K. H. Schweikert, F. Noack)....Pages 458-459
A Mosfet Transmission-Line High-Power ENDOR Spectrometer (A. Colligiani, G. Romanenghi)....Pages 460-460
A Nonlinear Interferometer for Measurement of 1D and 2D Interferograms in NMR and ESR Spectroscopy (J. Paff, B. Blümich, G. Hölz, G. G. Maresch, V. Macho)....Pages 461-462
Simple, Low-Frequency, Short-Recovery Double Coil Probe for Acoustical NMR (G. Floridl, R. Lamanna, P. Diodati, S. Cannistraro)....Pages 463-464
Front Matter ....Pages 465-465
Nuclear Spins as Probes for Conduction Electrons (Gert Denninger)....Pages 466-467
Near Bandgap Photoemission of Polarized Electrons in Semiconductors (C. Hermann, H.-J. Drouhin, G. Lampel)....Pages 468-470
NMR Studies of Diffusivity and Spin-Lattice Relaxation of Protons and Deuterons in Tantalum (M. Hampele, G. Majer, R. Messer, A. Seeger)....Pages 471-472
Knigt Shift and Diffusion in Solid Lithium and Sodium at Pressures up to 8 GPA Studied by NMR (R. Bertani, M. Mali, J. Roos, D. Brinkmann)....Pages 473-474
Tunneling and Spin-Lattice Relaxation of Hydrogen Dissolved in Scandium Metal (I. Svare, D. R. Torgeson, F. Borsa)....Pages 475-475
High Resolution 13C NMR Investigation of the Organic Conductor DMTM (TCNQ)2 (F. Rachdi, M. Ribet, T. Nunes, P. Bernier, M. Almeida)....Pages 476-476
Paramagnetism of Small Metal Particles Studied by NMR (J.-J. Bercier, J.-P. Bucher, Yuye Tong, J. J. van der Klink)....Pages 477-478
Anomalous Field Dependence of the Second Moment in Bi Observed by µSR (P. Birrer, F. N. Gygax, B. Hitti, E. Lippelt, A. Schenck, M. Weber)....Pages 479-480
Muon Tunneling and Spin Relaxation in Iron (Ivar Svare)....Pages 481-481
The 145Nd NMR in Magnetic Nd - Co Compounds (H. Figiel, N. Spiridis, Cz. Kapusta, J. Ƶukrowski, P. C. Riedi, R. Graham)....Pages 482-483
Pulsed NQR in Metallic Arsenic under Pressure (J. M. Keartland, M. J. R. Hoch)....Pages 484-485
Magic Angle Sample Spinning NMR Studies of a Diluted Magnetic Semiconductor Alloy: Cd1-xMnxTe (D. Zamir, Kebede Beshah, P. Becla, R. G. Griffin)....Pages 486-486
Nuclear Magnetic Resonance Study of 57Fe in Zn2Ba2Fe12O22 Hexagonal Ferrite (J. Hankiewicz, Z. Pajak, A. A. Murakhowski)....Pages 487-488
(Zr-Ni)1-x-yPxHy Double Resonance in a Glassy Metal (G. Lasanda, K. Tompa, A. Werner, P. Bánki)....Pages 489-489
Spin Resonance of Positive Muons in α-Iron at High Temperatures (M. Hampele, G. Majer, J. Major, H. P. Raich, R. Roth, A. Seeger et al.)....Pages 490-491
NMR Characterization of Singlet-Ground State Compound Thulium Dihydride. (H. Winter, D. Shaltiel, E. Dormann)....Pages 492-493
Pulsed Field-Gradient (PFG) NMR Study of Self-Diffusion in Liquid Sodium (Thomas Pfiz, Alfred Seeger)....Pages 494-495
Diffusion in Superionic β - Ag3SI Studied by Chemical Shift Relaxation. (M. Hertwig, J. Roos, M. Mali, D. Brinkmann)....Pages 496-497
NMR-study of molecular dynamics in some proton and organic conductors. (L. N. Erofeev, V. G. Shteinberg, B. A. Shumm)....Pages 498-498
(TMTSF)2(2,5-DBr-DCNQI) A CT-Complex with Magnetic and Electrical Properties Attributed to Different Stacks (S. Söderholm, J. U. von Schütz, G. Schaumburg, H. W. Helberg, P. Erk, S. Hünig)....Pages 499-500
Proton- and Alkali(X=Li,Na,Rb)-Spinrelaxation and Knight-Shift Measurements on Conducting (DCNQI)2X Salts (M. Bair, J. U. von Schütz, H. C. Wolf, P. Erk, H. Meixner, S. Hünig)....Pages 501-502
Pulsed ESR Studies on Low Dimensional Organic Conductors (M. Krebs, J. U. von Schütz, H. C. Wolf)....Pages 503-504
The Dimensionality of Spin Carrier Transportation: A Comparison of 3-D Cu-DCNQI with 1-D TI-DCNQI by ESR and NMR (U. Langohr, J. U. von Schütz, H. C. Wolf, S. Hünig, H. Meixner)....Pages 505-506
Front Matter ....Pages 507-507
High Frequency ESR: From Spectral to Spatial Resolution (Ya. S. Lebedev)....Pages 508-509
Molecular Dynamics and Phase Transitions in Solids Studied by ESR (Jan Stankowski)....Pages 510-510
113Cd NMR Study of Cd2+-Substituted Bovine Carbonic Anhydrase B (A. Olivson, J. Jarvet, R. Aguraiuja, R. Teeäär, E. Lippmaa)....Pages 511-511
Towards 3D Exchange NMR in Solids (K. Schmidt-Rohr, H. W. Spiess)....Pages 512-513
Broken Symmetry States of Rotating Molecules in Solids (S. Clough)....Pages 514-515
Deuterium Quadrupole Echo and Carr-Purcell Echo Relaxation in Chemically Exchanging Systems (K. Müller, R. Poupko, Z. Luz)....Pages 516-517
The Study of Molecular Tunnelling by Low-Field Dipole-Dipole Driven NMR Spectroscopy (A. J. Horsewill, A. Aibout, S. Clough)....Pages 518-519
Methyl Group Dynamics in α-Crystallized Toluene as Studied by 2H-Spin Lattice Relaxation (D. van der Putten, G. Diezemann, F. Fujara, H. Sillescu)....Pages 520-521
Topology, Spin-Density Distributions, and Spin Alignment in Organic High-Spin Molecules as Studied by Endor (Y. Teki, M. Okamoto, K. Sato, T. Takui, T. Kinoshita, K. Itoh)....Pages 522-523
Relaxation Rates in Slow-Motion Regime: Application to Methyl Groups Near Level Crossing (M. Punkkinen)....Pages 524-524
An NMR Study of Hydrogen Bond Dynamics (A. J. Horsewill, A. Aibout, A. Heidemann, S. Hayashi)....Pages 525-526
In-Vivo NMR Studies of the Grains of Oat (R. Lenk, R. Degli Agosti, H. Greppin)....Pages 527-528
Stable Radical Pairs in Single Crystals of Hindered Phenols as Spin Probes to Study Organic Crystals (G. G. Lazarev, V. L. Kuskov, Ya. S. Lebedev)....Pages 529-530
Single Crystal ESR Studies of Transition metal (o-Benzene-Diselenolate) 2- [BDS] and (o-Benzenedithiolate) 2- [BDT] Complexes: Potential Synthetic Metal Precursors (M. Thomas Jones, Megh Singh, James H. Roble, Toshio Maruo)....Pages 531-532
The 1H, 2H, and 17O NMR Study of Hydrogen Bond Exchange in Carboxylic Acids (V. Balevicius, L. Kimtys)....Pages 533-533
Endor Determined Structure and Conformation of Spin-Labeled Methyl L-Phenylalanate in Frozen Solutions (Heikki Joela, Devkumar Mustafi, Marvin W. Makinen)....Pages 534-535
EPR and Optical Studies of Dysprosium in Lanthanide Nicotinate Dihydrates (J. M. Baker, C. A. Hutchison Jr., M. J. M. Leask, P. M. Martineau, M. G. Robinson, A. L. Tronconi et al.)....Pages 536-537
Quadrupole Effects with Anomalous Temperature Dependences in 127 I-Solid State NMR of (n-C4H9) 4 AsIO4 and (n-4H9) 4 PIO4 (P. K. Burkert, T. Pietraß)....Pages 538-539
Chemical Shift Anisotropy of 13C Nuclei in Carbonyl Groups of Metal Carbonyl Complexes (Adam Gryff-Keller, Hanna Krawczyk, Przemysław Szczeciński)....Pages 540-541
The 10B- and 11B-Nuclear Quadrupole Coupling of P-Carborane (A. Lötz, J. Voitländer)....Pages 542-543
Dynamics of Water Molecules in MgSO4·1H2O Studied by NMR (J. Murín, J. Uhrin, M. Királ’varga, K. Jelšovská)....Pages 544-545
The 14N NQR Spectrum and the Crystal Structure of Ba [Fe(CN)5NO] · 3H20 at Room Temperature (Juan Murgich, Ismardo Bonalde)....Pages 546-547
High-Field Multinuclear NMR Studies on Trimethylacetic Acid (D. W. Aksnes, L. L. Kimtys)....Pages 548-549
2D NMR Relaxation Spectroscopy of Molecular Solids (K. Müller, A. Schleicher, G. Kothe)....Pages 550-551
Proton Spin-Lattice Relaxation in Fe/py/3Cl3·py (J. Kasprzak, M. Januszczyk, J. Pietrzak, L. Ševčovič)....Pages 552-553
New Approach to Calculate the Echo Shape in Solids with Molecular Motions (N. A. Sergeev, D. S. Ryabushkin, A. V. Sapiga)....Pages 554-555
Water Proton Spin-Lattice Relaxation and Self-Diffusion in Protein Solutions (R. Lamanna, S. Cannistraro)....Pages 556-557
Cation Dynamics in High Temperature Phase of Pyridinium Tetrafluoroborate (M. Buszko, Z. Pająk, J. Wąsicki, J. Tegenfeldt)....Pages 558-559
Theory of Intercorrelation Between Dipolar and Quadrupolar Fluctuations:Application to 2H NMR in Clays (D. Petit, J.-P. Korb, A. Delville, J. Grandjean, P. Laszlox)....Pages 560-561
Electron Spin Resonance Linewidth Studies of Vanadyl Tetraphenylporphyrine (Ali H. Al-Mowali, Alhan D. Girgees)....Pages 562-562
The Relative Intensities of Level Crossing Transitions in the Rotational Tunnel Spectrum of NH4 in Partially Deuterated Ammonium Persulphate (M. Johnson)....Pages 563-564
ESR and Structure of Vanadic(IV)-Thallium(I) Heteropolynuclear Dithiocarbamate Complexes (P. M. Solozhenkin, A. V. Ivanov, Z. R. Baratova)....Pages 565-566
The Temperature Dependence of the Correlation Time of Slowly Tunneling Methylgroups, Derived from Spin Conversion and Spin-Lattice Relaxation Measurements (A. Buekenhoudt, L. Van Gerven)....Pages 567-568
Pulsed ESR and Molecular Motions (Yu D. Tsvetkov, S. A. Dzuba)....Pages 569-569
Triplet Electron Transfer in Covalently Linked Porphyrin-Quinones Detected with Time-Resolved EPR (F. Lendzian, B. von Maltzan, J. Schlüpmann, M. Plato, J. von Gersdorff, H. Kurreck et al.)....Pages 570-571
2H-NMR Stimulated Echo Study of Ultraslow Reorientational Motion in Viscous Glycerol Near its Glass Transition Temperature (R. M. Diehl, F. Fujara, H. Sillescu)....Pages 572-573
NMR of Paramagnetic Metals Complexes with Stable Imidazoline Nitroxide Radicals (A. M. Atskanov, A. B. Burdukov, A. A. Savelov, V. I. Ovcharenko, A. V. Podoplelov, R. Z. Sagdeev)....Pages 574-574
Orientation Selected Endor Studies of a Manganese Dimer (M. Baumgarten, J. S. Sheats, G. C. Dismukes)....Pages 575-576
Multiaxis Reorientation of ND4+ Ions: New Sequential Model (Z. T. Lalowicz, S. F. Sagnowski, M. Punkkinen, E. E. Ylinen)....Pages 577-578
Molecular Dynamics in [N(CH3)4]3Bi2Cl9 (W. Medycki, N. Piślewski)....Pages 579-580
Test of Pseudo-Spin Theory of Ammonium Scheelites (R. J. C. Brown, D. R. Taylor, F. P. Temme, B. M. Powell)....Pages 581-581
17O NMR Studies of Solid Amino Acids (D. Fiat, J. Tritt-Goc, R. Goc)....Pages 582-583
A Determination of the Dynamical Parameters in Amino Acids from Carboxylic- 17O NMR Linewidths Measurements (J. Tritt-Goc, D. Fiat)....Pages 584-585
Proton Magnetic Relaxation Investigations of Molecular Dynamics in Ferroelectric [(CH3)3 NH]3Sb2Cl9 (B. Jagadeesh, P. K. Rajan, K. Venu, V. S. S. Sastry)....Pages 586-587
NMR of Noble Gases in Liquids (A. V. Il’yasov, K. M. Enikeev, R. K. Masitov)....Pages 588-589
EPR of Copper(II) Complexes with Indomethacinum and Ibuprophenum Ligands (O. Cozar, I. Bratu, I. Ardelean, S. Simon, V. Znamirovschi, Gh. Bora)....Pages 590-591
The Study of Intercalated Molecules Using One- and Two-Dimensional Solid-State NMR (M. J. Duer, J. Klinowski, J. Rocha)....Pages 592-593
Structure Determination of a Norbornane-Norbornene-Fused Pentacyclic Isoxazoline by NMR Spectroscopy (Pál Sohár, István Kövesdi, Géza Stájer, Gábor Bernáth)....Pages 594-594
NMR Studies on Complexation in Penicillin Solutions (Teobald Kupka, Jan O. Dzięgielewski)....Pages 595-595
31P NMR Studies on (β-Naphthoxy)Cyclotriphosphazene Derivatives with Various Degree of Substitution (K. Brandt, T. Kupka)....Pages 596-597
Molecular Dynamics in Dimethylmalonic Acid Crystal as Studied by NMR (S. Idziak, N. Piślewski)....Pages 598-599
Generation of Large Scale Patterns in Ferromagnets Under the Influence of High Frequency Force (I. V. Bar’yakhtar, A. V. Tur, V. V. Yanovsky)....Pages 600-601
NMR Study of Molecular Motions and Phase Transitions in (CH3) 3NHPbX3 (X=Cl,Br,I) (D. Vijayaraghavan, J. Ramakrishna)....Pages 602-603
FT-ESR Investigation of Photo-Induced Charge Transfer in the ZnTeraphenylporhyrin/Duroquinone System (K. P. Dinse, M. Plüschau, G. Kroll, H. van Willigen)....Pages 604-604
Solid State Deuterium NMR Studies of β-Cyclodextrin-Drug Inclusion Complexes (T. K. Halstead, S. J. Kitchin, G. D. Parr)....Pages 605-606
35Cl NQR and Structure of Methylanilinium Chloroacetates (R. Basaran, S. Q. Dou, Al. Weiss)....Pages 607-608
Studies on 1,2,3,-Trichloropropane in the Solid Phase (Mariano J. Zuriaga, Gustavo A. Monti, Carlos A. Martín)....Pages 609-609
A Nuclear Quadrupole Resonance Study of the Solids 2,3,6-Tri Chloroanisole, 2, 4, 6-Trichloroanisole and p-Chloroanisole (Ariel A. Pertile, Carlos A. Martín, Máximo E. Ramia)....Pages 610-611
An ESR-ENDOR Study of Molecular Motions of Long-Chain Ketone/Urea Inclusion Compounds (M. Brustolon, A. Ferrarini, A. L. Maniero, P. L. Nordio, U. Segre)....Pages 612-612
Deuteron NMR Study of Molecular Motion near the Glass Transition in Polystyrene at High Pressure (A. S. Kulik, M. de Langen, K. O. Prins)....Pages 613-613
Study of Methyl Group Tunneling with Low Field NMR (M. Van Cleemput, M. Bruggeman, L. Van Gerven)....Pages 614-614
14N and 1H Spin-Lattice Relaxation in Solid 3,5-Dimethylpyrazole (F. Aguilar-Parrilla, H.-H. Limbach, M. Blanz, T. J. Rayner, J. A. S. Smith)....Pages 615-616
Front Matter ....Pages 617-617
Second Quantization Method in Two-Dimensional NMR Spectroscopy (W. Nosel, P. S. Allen)....Pages 618-618
Aspects Of SU2 × ϕn Liouvillian Duality and SU2/SO(3) × (ϕ12↓ A5) Symmetry Over Spin (Spin-Isomorphic) Spaces Of MO-NMR and Ouantum-Rotational Tunnelling Problems (J. P. Colpa, F. P. Temme)....Pages 619-620
Unusual Behaviour of the Indium Hyperfine Interaction of FeIn Pairs in Silicon (W. Gehlhoff, P. Emanuelsson, P. Omling, H. G. Grimmeiss)....Pages 621-622
Special High-Power Probes for Solid-State NMR Investigation (G. Scheler, Chr. Jäger, B. Blümich, K. Schmidt-Rohr)....Pages 623-623
EPR of Mn2+ Ions with Different Trigonal Zero-Field Splitting: The Mn2+-Acceptor Pairs in Silicon (J. Kreissl, W. Gehlhoff)....Pages 624-625
14N Nuclear Quadrupole Resonance Dips in the Proton Relaxation Dispersion of Nematic and Smectic Liquid Crystals (D. J. Pusiol, R. Humpfer, F. Noack)....Pages 626-627
Evidence of a Four-Magnon Instability in a Yig Slab by Photothermally Detected FMR (S. A. Nikitov, O. v. Geisau, J. Pelzl)....Pages 628-629
31P-NMR Investigations of Crystalline Hydrogen Phosphates (P. Hartmann, B. Schnabel, J. Vogel)....Pages 630-631
On Time Dependence of Magnon Damping in Short Pulses (V. B. Cherepanov)....Pages 632-632
Field-Modulated Microwave Absorption in Granular Superconductors: First and Second Harmonic Signals (M. Požek, A. Dulčić, B. Rakvin)....Pages 633-634
Back Matter ....Pages 635-642

Citation preview

M. Mehring J.U. von Schutz H.C. Wolf Editors

CONGRESS AMPERE ON

MAGNETIC RESONANCE AND

RELATED PHENOMENA Extended Abstracts

STUITGART 1990

Springer-Verlag Berlin Heidelberg New York London Paris Tokyo Hong Kong Barcelona

Michael Mehring lost Ulrich von Schiltz Hans Christoph Wolf PhysikaIisches Institut, Universitit Stuttgart Pfaffenwaldring 57, D-7000 Stuttgart 80 Fed. Rep. of Germany

ISBN-l3: 978-3-540-53136-4 DOl: 10.1007/978-3-642-76072-3

e-ISBN-13: 978-3-642-76072-3

This work is subject to copyright. AlI rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in other ways, and storage in data banks. Duplication of this publication or parts thereof is only permitted under the provisions of the German Copyright Law of September 9, 1965, in its current version and a copyright fee must always be paid. Violations fall under the prosecution act of the German Copyright Law.

o Springer-Verlag Berlin Heidelberg 1990 The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. 2154/3140-543210

v

PREFACE

The 25th CONGRESS AMPERE on Magnetic Resonance and Related Phenomena is being held at the University of Stuttgart, Federal Republic of Germany, September 9 - 14, 1990. More than 420 scientific participants from more than 30 countries are attending the congress. The scientific program, which covers the full range of magnetic resonance and radiospectroscopy and its application in physics, chemical physics, medicine and biology, consists of ten plenary lectures and 27 specialized symposium lectures. In addition, 300 contributed papers will be presented. The extended abstracts of these lectures are collected in this book which constitutes also the Proceedings of the 25th CONGESS AMPERE. This procedure was initiated at the 18th CONGRESS AMPERE in Zurich and we believe it to be the most timely and effective way of communicating scientific information. This book is available at the beginning of the conference. Mter the opening ceremony, Professor K.H. Hausser will hold a laudatio on the first AMPERE prize winner, Professor Richard Ernst, who will present the prize winner lecture, entitled: '7empora mutantur, NMR et mutatur in illis". This is indeed the motto of the following lectures which demonstrate once again that magnetic resonance is as vital as ever and has proven to be one of the most versatile methods in such diverse areas as atomic, molecular and solid state physics, physical chemistry, photosynthesis, chemistry and biology, material science as well as medicine. Although a large number of specialized conferences are being held on these subjects, still a large number of scientists gather to take part in the CONGRESS AMPERE. This book is a witness of this continuing activity. The Congress is held under the patronage of Dr. Lothar Spath, Ministerprasident des Landes Baden-Wurttmberg. A reception by the Land Baden-Wurttemberg and the City of Stuttgart will take place in the Neues SchloG. Over two hundred participants will gather for the Congress Dinner in the Haus der Wirtschaft in downtown Stuttgart, where Professor GJ. Bene., the former Secretary-General of the Groupement Ampere will present an after-dinner speech on the past and future developments of the Groupment Ampere. An excursion to the Burg Hohenzollern, a famous castle south of Stuttgart and several day-time social programs take place during the congress. The 25th CONGRESS AMPERE received sponsorship from the Deutsche Forschungsgemeinschaft, the Land Baden-Wiirttemberg, the Deutsche Akademische. Austauschdienst and the following companies: Baden-Wurttembergische Bank Stuttgart, BASF AG. Ludwigshafen, Bayer AG. Leverkusen, Robert Bosch GmbH. Stuttgart, Broker MeGtechnik Rheinstetten, Daimler Benz AG. Stuttgart, Deutsche Bank AG. Stuttgart, Dresdner Bank AG. Stuttgart, Hoechst AG. Frankfurt, IBM Deutschland Stuttgart, E. Merck Darmstadt, Siemens AG Munchen and Spectrospin AG Switzerland.

VI

The organizational part of the conference was in the hands of the scientific secretary Dr. J.U. von Schiitz. On behalf of the Organizing Committee we wish to express to everyone who helped in the successful organization of the 25th CONGRESS AMPERE at Stuttgart our most cordial thanks for their hard work, enthusiasm and co-operation. We would like to add a further personal word of thanks to Dr. J.U. von Schutz and all our colleagues on the Organizing and Program Committee for their tremendous efforts and their friendly collaboration during the preparation time prior to this congress.

September 9, 1990

M. Mehring and H.C. Wolf Chairman-Organizing Committee 25th CONGRESS AMPERE, Stuttgart

VII

COMMITIEES Organizing and program committee

Bureau Amp~re

B. Elschner KH. Hausser G. Kothe M. Mehring (Chairman) F. Noack J.U. von Schutz (Secretary General) D. Schweitzer H.C. Wolf (Chairman)

R B. R GJ. Y. KH. G.

Blinc (President) Maraviglia (Vice President) Kind (Secretaire General) Bene (Secretaire General Sortant) Servant (Secretaire Executit) Hausser (president Sortant) Raoult (Secretaire Executif Sortant)

INTERNATIONAL ADVISORY BOARD The members of the Committee Ampere

E.R Andrew (USA) G.J. Bene (Switzerland) R Blinc (Yugoslavia) AS. Borovik-Romanov (UDSSR) RR Ernst ( Switzerland) R Freymann (France) M. Goldman (France) E.L Hahn (USA) KH. Hausser (F.RGermany) J. Hennel (poland) S.K Hoffmann (Poland) O. Jardetzky (USA) R Kind (Switzerland) B.I. Kochelaev (UDSSR) E. Lippmaa (UDSSR) A LOsche (DDR) Z. Luz «(Israel) M. Maraviglia (Italy) AF. Martins (portugal) F. Milia (Greece)

KA Muller (Switzerland) A Pines (USA) M. Punkkinen (Finland) G. Raoult (France) A Rigamonti (Italy) R Sagdeev (UDSSR) Y. Servant (France) J. Schmidt (Netherlands) M. Schwoerer (F.RGermany) C.P. Slichter (USA) H. Sterk (Austria) J. Spevacek (CSSR) H.W.Spiess (F.RGermany) I. Svare (Norway) J. Tegenfeldt (Sweden) K Tompa (Hungary) I. Ursu (Romania) L van Gerven (Belgium) W. Windsch (DDR) A Zheliaskova (Bulgary)

VIII

GENERAL CONTENTS

Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V Organizing and Program Committee •••••••••••••••••••••••••••••••• vn Bureau Amp~re • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• vn Advis~I")' Board ................................................ VII Detailed Contents .............................................. IX

Extended Abstracts Plenary Lectures (invited) ••••••••••••••••••••••••••••.••.•••••••• Invited and contributed Papers Excitations and Defects Amorphous and Disordered Solids Imaging ..................................................... . Spindynamics Photoexcitations and Photosynthesis •••••••••••••••••••••••••••••••• Spin Polarization and Relaxation Application ••••••••••••••••••••••••••••••••••••••••••••••••••• Superconductors ••••••••••••••••••••••••••••••••••••••••••••••• Liquid Crystals and Polymers Phase Transitions New Methods Conductors and -Semiconductors ••••••••••••••••••••••••••••••••••• Molecular Structure and Dynamics ••••••••••••••••••••••••••••••••• Post Deadline Contributions •••••••••••••••••••••••••••••••••••••• List of Authors •••••••••••••••••••••••••••••••••••.••••••••••••

1 19

55

87

117

155

179 229 243 303 373 413 465 507 617 635

IX

DETAILED CONTENTS

Plenary Lectures (invited) "Experiments with an Isolated Subatomic Particle at Rest" H. Dehmell

(page 2)

"NMR Study of Charge Density Waves" C. Berthur, P. Segransan, P. Buraud, and A. Janossy

(page 3)

"NMR Imaging: Current Status and Future Prospects" P. Mansfield, R.J. Coxon, D.N. Guilfoyle, A.M. Blamire, P. Gibbs, P. Harvey, and M.

Symms

(page 1)

"ESR-Experiments on the Two-Dimensional Electron Gas of Heterostructures" K. VOII Klitring, M. Dobers, and A. Berg

(page 9)

"Muon Spin Rotation Experiments in Solids" H. KeUer

(page 12)

"NMR with Adsorbates on Solid Surfaces" D. Pick

(page 14)

"New Approaches in Time-Domain ESR for the Study of Molecular Structures" A. Schweiger

(page 15)

EXCITATIONS AND DEFECTS

Symposia Lectures (invited) "ODMR of Defects in Semiconductors" I.M. Spaeth

(page 20)

Lectures "14N ENDOR of the W7 Centre in Natural Type Ia Brown Diamond" I.M. Baker, and M.E. N e w t o n '

(page 22)

"Time Resolved EPR Studies of Phenazine-TCNQ and Biphenyl-TCNQ Excited Triplets" C. Corvoja, L. Pasimeni, and A. Toffoletti (page 24) "High-Spin Multiplet ENDOR and Triple Resonance: Its Application to a Model Compound for Organic Ferrimagnets" T. Takui, M. Endoh, S. Kila, Y. Teki, T. Kinoshita, and K. ltoh (page 26) "Local Deformation and Hyperfine Fields on the Ligands in Trigonal Centre Yb3+ in KMgF3" M. V. Eremin, M.M. Zaripov, I.R. lbragimov, M.P. Rodionova, and M.L. Falill (page 28) Posters "Spin-Lattice Relaxation of F+-Centers in Neutron Irradiated CaO Crystals" G. Liidja, and T. Room

(page 30)

"ESR-Investigations on the Solid Solution Mg2.xCuxP4°12" W. Gunfter, and A. ZimmeT71UJ1I1I

(page 32)

"Doping Effect and I(V) Characteristic as Found by ESR" N. Rieux, J. Pescia, Bui Ai, and Y. Servant

(page 34)

x "Optical Detection of Cross-Relaxation of F-Centres and Paramagnetic Impurities in Alkali Halides" P.G. llorruwv, V. V. Dyakonov, N. G. Romanov, and V. V. Vetrov (Page 36) "Point Defects in Copper Studied by Nuclear Quadrupole Double Resonance Using the FieldCycling Technique" M. Bltuu., M. Hampele, G. Majer, M. Nolter, and A. Seeger (page 38) "Anharmonic Electron Spin-Lattice Relaxation of the Irradiational Defects in Potassium Selenate and Rochelle Salt Single Crystals" (Page 40) V.A. lvanshin, I.N. Kurkin, W. Brunner, and G. Vlilkel "The Influence of the Interionic Distance on the Cubic EPR Spectrum of Gdl + Ion in RbCaFl Single Crystals" T. R,waj (Page 42) "EPR of Mn + Centres in Ba.F2 and SrF2" P. G. Baranov, A. Ho/sta,tt,r, T. Nickel, A. Scharmann, and F. SchlJn "Light-Induced Changes in the FMR Parameters of CdCr2Se4"

E. Mosiniewicz-Szablewska

(Page 44) (Page 46)

"Elastical Deformation of Mg2Si04:Cr3+ (Forsterite) and MgO:Mn2+ and Fe3+ by Uniaxial Stress. An in situ EPR Study" R. Lueck, R. Stoesser, H. Rager, J. Klein, A. Rericha, and 5.5. Ha/ner (Page 48) "Antiferromagnetic Resonance in lahn-Teller KDy(MoO~2 Type Crystal" M.D. Kaplan

(Page 50)

"Field Induced Phase Transitions of Ferromagnetic Bilayers with Antiferromagnetic Coupling" w. Schmidt (Page S 1) "EPR Investigations of the Dynamics of Doping Ions in Perovskite Lead Titanate Ceramics" W. Windsch, R. Heidler, G. Klotzsche, and B. MUsch (Page 53) AMORPHOUS AND DISORDERED SOLIDS Symposia Lectures (invited)

Kan,,,

"Nuclear Spin Relaxation and Atomic Motion in Inorganic Glasses" O.

(Page 56)

Lectures "A Simple Method Analyzing NMR Line Shape of Mobile Probes in Disordered Solids" E. Rossler, K. BlJmer, M. Taupirz, H.M. Vieth, and M. Schulz

(Page 58)

"NMR Determination of Order Parameters in Quadrupolar Glasses" W. Wiotte, S. Elschner, J. Petersson, and R. Blinc

(Page 60)

"Electron Spin Resonance of Vitreous Thioborates" M. HaddIJd, R. Berger, Y. S,rvant, and A. Levasseur

(Page 62)

"EPR Study of Disorder and Phase Transitions in Rb1_xKxCaFl " P. Foucher, and J. Y. Bur.are

(Page 64)

XI

Posters "Spin-Lattice Relaxation in Silicate and Vanadate Glasses" T. Bouhacina, G. Ablart, M.R. Pilod, J. Pescia, and Y. Servant "New Interpretation of Diffusion and Relaxation Processes in Amorphous Materials"

1. PocsiJc

"Interpretation of the Asymmetry of NMR Spectral Lines in Amorphous Materials"

1. PocsiJc

"Cluster Selective Relaxation Behaviour in the Deuteron Glass Rbo.S6(ND4)O.44D2P04"

N. Korner, J. Dolinsek, and R. J{jnd

(Page 66) (Page 68)

(page 70) (Page 72)

"Two-Dimensional NMR Separation of Inhomogeneous vs. Homogeneous Lineshapes in the Glassy State: 87Rb in Proton Glass DRADP" J. Dolinsek (page 74) ·Solid State NMR Spectra of Microporous Aluminophosphates" P.J. Grobet, H. Geerts, J.A. Martens, and P.A. Jacobs

(page 76)

"Ferroelastic Domain Structure in Incommensurate Phase in Trigonal Double Molybdates and Tungstates· w. Zapart, and M.B. Zopart (Page 78) "Nonexponential 2H-NMR Spin-Lattice Relaxation as a Signature of the Glassy State" W. Schnauss, F. Fujara, K. Hartmann, and H. Sillescu

(page 80)

"The Partial Crystallization Effect on the EPR Spectra from Bi-Sr-Ca-Gd-Cu-O Vitreous Matrices" S. Simon, O. Couzr, I. Barbur, V. Simon, I. Artielean, Gh. Ilonea, and V. Ioneu

(Page 82)

"The Valence States and Interaction Between Chromium Ions in Lithium-Borate Glasses"

O. Co%QT, I. Artielean, Gh. I/onea, S. Simon, I. Barbur, and I. Bratu

(Page 84)

"Results of High-Field 31P_NMR Investigations of the Crystalline and Amorphous Phosphats Systems with Increased Spectral Resolution" B. Schnabel, P. Hartmann, and P. Losso (Page 86) IMAGING

Symposia Lectures (invited) ·NMR-Microscopy: Principles, Limits and Applications· W. Kuhn

(Page 88)

"Nuclear Magnetic Resonance Imaging of Solids with Magic Angle Spinning" W.S. Veeman

(Page 90)

·Stray-Field Imaging of Solids (STRAFI)" K. Zick, and A.A. Samoilen1co

(Page 92)

XII

Lectures -Detection of Chemical Waves by Magnetic Resonance ImagingR.L. Armstrong,". TzoJmona, M. Menzinger,". Cross, and L. Lemaire

(Page 94)

-Nondestructive Evaluation of Polymer Compounds by Solid State NMR ImagingP. Blilmler, E. Ganlher, G. Sc1uluss, H. W. Spiess, and B. Blumieh

(Page 96)

-NQRI . gB. Romm~. Nickel, R. Kimmich, and D.l. Pusiol

(page 98)

-Imaging of Solids by Audio Frequency Excitation in the Rotating FrameF. De Luca, B. C. De Simone, P. Fattibene, N. Lugeri, and B. Maraviglia

(page 1(0)

Posters -NMR Microscopy of Plant Systems at 11.7 r R. BowteU, G. Brown, P. Glover, M. MeJury, and P. Mansfield

(Page 101)

-EPR Imaging Applications in Solid Polymers-

J. DtUam, V. Macho, G. G. Maresch, D. Davidov, and H. W. Spiess

(Page 103)

-NMR Imaging and Volume-Selective Spectrosocpy in Solids: Product Operator Formalism and Test ExperimentsS. Hqfner, E. Rommel, and R. Kimmich (page lOS)

-Response to Tip-Angle and Spin-Lock RF Pulse Sequences in the Presence of Magnetic Field Gradients: Slice-Selective ExCItation in NMR Imaging ExperimentsD.E. Demeo, F. Balibanu, and R. Kimmich (page 107) -On the Proton T2 Effects of Oxygen-I7 as an NMR and MRI Label for Water in Living SystemsA.L. Hopkins, E.M. Haacke, W.D. LUSI, P.". Wielopolski, R.G. Barr, and C.B.

Brtllton

.

(Page 109)

-Double Resonance Rare Nuclei ImagingF. De Luca, R. Campanella, A. Bi/one, and B. Maraviglia

(Page 111)

-Perspectives of the Use of Magnetically Labeled Antibodies in NMR ImagingM.A. Macri, F. De Luca, G. Garreffa, and B. Maraviglia

(Page 112)

-Imaging of 7Li in a Polymer Electrolyte Film PEOs(LiClo,J: A Preliminary InvestigationM. Sondengger, 1. Roos, M. Mali, and D. Brinkmann (Page 113) -Spatially Resolved Tl Relaxation Measurements of Brine in Rock Cores-

JJ. AIIIud, T.". CarpenJer, and L.D. Hall

(Page 115)

-Localized NMR Spectroscopy with a I.S T Whole Body ImagerW.-l. lung, O. Lut:, K. Maller, M. Pfeffer, M. Riec/cen, and F. Schick

(Page 116)

SPINDYNAMICS Symposia Lectures (invited) -Creation, Migration and Observation of Longitudinal Multiple-Spin OrderG. Bodenhau.en

(Page 118)

XIII

Lectures "Quadrupolar Echoes on Spin I> 1 Nuclei" 1. FurO, and B. Halle

(Page 120)

"NMR Studies of Double Proton and Deuteron Transfers in Liquids and Solids" H.H. Limbach, H. Rumpel, B. Wehrle, L. Meschede, M. Schlabach, G. Scherer, J. Braun, F. Aguilar-Parilla, and C. Hoelger

(page 121)

"Transfer of Spin Order in Solids. Deterministic and Diffusive Behavior" G. Aebli, B.H. Meier, and R.R. Ernst

(page 123)

"Multiple Spin Echoes in a Liquid in a High Magnetic Field" R. BowteU, R.M. Bowley, P. Glover, and A. Bedford

(page 124)

"NMR Line Shape in Solids"

E.l. Fedin

(page 126)

Posters "FSR Lineshape for Exchanging Anisotropic Spin Systems" N.P. Benetis, R. Erickson, Lars SjlJqvi.st, and A. Lund

(page 127)

"Cross Polarization to Low-t"Nuclei" A. Sebald, and L.H. Merwin

(Page 129)

"High-Resolution Solid-State NMR Spectroscopy of Heavy Spin-I12 Nuclei: Interactions with Neighboured Quadrupolar Nuclei" A. Sebald (Page 130) "Phonon Contribution to the AFMR Linewidth of a Heisenberg Antiferromagnet" T.J. Drye, and J. W. Tucker "EPR of Solitons in One-Dimensional Antiferomagnets"

(page 131)

J. Kuriata, L. Sadlowski, B. Bojanowski, and M. Wabia

(Page 133)

"FSR Pumping of Atomic Hydrogen Gas at Low Temperatures" A. Ya. Katunin, S.A. Vasilyev, and 1.1. Lukashevich

(page 135)

"Multiple Spin Echo Signals in Systems with Mutual Quadrupole" T.Sh. Abesadze, and R.A. El-egaimi

(page 136)

"Nuclear Spin Echo Amplification in Magnetics, Caused by Resonator Effects" N.P. FoldlUl, and K. O. Khutsishvili

(page 138)

"Orientation Selective FSEEM of Nitrogen Coordinated Oxo-Vanadium (IV) Complexes" E.J. Reijerse (page 140) "Memory Effects in the Problems of Magnetic Resonance and Magnetic Relaxation" R.R. Nigmatuilin, and D.A. Tayursldi

(Page 142)

"Cross-Relaxation in Paramagnetic Crystals at Low Temperatures" D.A. Tayursldi

(Page 144)

"Multiple-Quantum NMR Spectrosocpy of Half-Integer Quadrupolar Nuclei in Rotating Solids" N.C. Nielsen, H. Bildsoe, and H.J. Jakobsen (page 146) "Dihydrogen Addition Studies by the Pasadena Effect" C.R. Bowers, P.J. Carson, D.J. Norris, and D. Weitekamp

(page 148)

XIV

-00 Threshold of Parametric Instability of Spin Waves in a Film with Rough SurfaceV.B. Ch'rqHIIIO'V -Spin-Wave Theory of NMR in Solids at Low Temperatures-

(Page 150)

E.B. F,IdnuuJ, and A.K. Khitrin

(Page 151)

-Propagation and Trapping of Phonons in Solids with Resonant Paramagnetic CentersB.1. Koc'h,Ion, A.E. Solovyev, and D. V. Chystyakov

(Page 153)

PHOTOEXCITATIONS AND PHOTOSYNTHESIS

Symposia Lectures (invited) " A Magnetic View of the Reaction Center" J.R. Norris

(Page 156)

"Magnetic Resonance of the Triplet State of Carotenoids in Photosynthesis"

A. Ang,mo/er, and V. Aust

(Page 158)

"Electron Spin Echo Studies of Nonradiative Molecular Triplet States" E.J.J. Gro,n,n

(Page 160)

Lectures "A Novel Radical-Triplet Pair Mechanism for CIDEP of Free Radicals" C. BlIJttler, F. Jent, and H. Paul

(Page 162)

-Time Resolved ESR Studies of Photoinduced Spin Correlated Radical Pairs in Photosynthetic Reaction Centres" A.J. WIn der Est, C.H. Bock, 1. Sieckmann, and D. Stehlik (Page 164)

.

"Dipolar Relaxation Enhancement in Inhomogeneous Systems. Application to the Oxygen Evolving Complex of Plant Photosynthesis" R.G. Evelo, and A.J. HoI/ (Page 166) -Transient EPR of Spin Polarized Triplet States and Correlated Radical Pairs in Viscous Uquid Crystals" R. BiJtl, N. RiJsch, S. Weber, A. MQnzenmaier, and G. Kothe (Page 167) Posters "Magnetic Resonance and Photochemistry: The Red-Photolysis of Solid Humulene NitrositeZ.F. KhiJn, D.K. MacAlpine, A.L. Pon" J.E. Schubert, and G.A. Sim (Page 169) -Novel Coupling Mechanism in Spin-Wave Instabilities" G. WUI', and H. Benner "ODMR Studies of Protein-Nucleic Acid Interactions"

D.H.H. TsQO, and A.H. Maid "ENDOR-Studi~ o~ P+ ~

(Page 171) (Page 173)

in Reaction Center Single Crystals of Rb. Sphaeroides R-26 at 8OC"

F. Lendzian, B. End.ewara, M. Plato, K. MlJbius, and W. Lubitz

(Page 175)

"RYDMR in Reaction Centers of Photosynthetic Bacteria" E. Lang, W. Lersch, R. Feick, W.J. Coleman, D. C. Youvan, and M.E. MichelBeyerle

(Page 177)

xv

SPIN POLARIZATION AND RELAXA nON

Symposia Lectures (invited) "Optical Spin Polarization and Spin Waves in Helium Three Gas" G. Vermeulen, and F. LaJoe

(page 180)

"Chemical Exchange and Quantum Exchange" D. WeiJekamp

(page 182)

"Stimulated Nuclear Polarization"

E.G. Bagryanskaya, I. V. Koptuyg, and R.Z. Sagdeev

(page 184)

Lectures "DNP and ESR at 5 T Fields"

T.F. PrUner, S. Un, R.T. Weber, A.C. McDermott, D.J. Singel, and R.G. Griffin

"Weak Field Dynamic Nuclear Polarization with Phosphorus Radicals" Y. Ayanr, N. Kernevez, L. Secourgeon, and P. TorOO "NMR-Investigations of Homogeneous Hydrogenation Reactions Using Para Hydrogen"

(page 186) (Page 188)

J. Bargon, J. Kandels, P. Kating, A. 17wmas, and K. Woelk

(page 190)

"ODENDOR of F-Centres without Microwaves and Thallium Impurity NMR in KCl:T1 Detected with the MDCA Technique" N.G. Romanov, D.M. Hofman, andJ.M. Spaeth

(page 192)

"31p

Relaxation Mechanisms in Phosphorus Metabolites"

E.R. Andrew, W.S. Brey, and R. Gaspar Jr.

(page 194)

"Dynamic Study of Glassy Properties of Deuteron Glass Rbl-x(ND4)xD2P04 Using 31p NMR Spin-Lattice Relaxation" S. Chen, and D.C. Ai1ion (page 196) Posters "Magnetic Resonance of Probe \'1)3+ and Er3+ Ions in the Antiferromagnetic Phase of DyP04" (Page 198)

J.M. Baker, B. Bleaney, A.A. Jenkins, and P.M. Martineau

"Contribution of Hydrogen Bonding (HB) to the Leakage Factor in Dynamic Nuclear Polarization (DNP)" M.P. Ferroud-Plattet, N. Kemevez, and Y. Ayant "19F-Spin-Lattice Relaxation of PF6 Intercalated in Graphite"

1. Stang, M. Kraus, and K. LOders

(page 2(0) (Page 202)

"Cu NQR and Li NMR Relaxation in the Paramagnetic Phases of CuO and Cu:O:Li"

A. LascUdfari, S. Aldrovandi, M. Fanciulli, F. Borsa, M. Corti, and A. Rigamonti

"Spin-Lattice Relaxation of Three-Spin System Through Intermolecular Dipole-Dipole Interaction" G. Slosarek

(Page 204)

(Page 206)

"Ab Initio Calculations of Zero-Field Splitting in Nickel(lI) Complexes: Implications for Electron and Nuclear Spin Relaxation" J. Kowalewski, M. Odelius, and C. Ribbing (page 207)

XVI

"Extremely Narrow Unes in the ESR Spectra at Longitudinal Double Modulation of a Magnetic Field" B.F. Alekseev, Ju. Bogachev, and A.B. 1ikhonov (Page 208) "Lanthanide (III) Ions Coordination and Water Mobility in Aqueous Solutions: Solvent Nuclear Magnetic Relaxation Study" V.I. Chidd/c, A. V. RlIsIwi, V. V. Matveev, and N.R. Skrynnikov (Page 210) "The Influence of Hydrolysis on the Quadrupole Relaxation of Monoatomic Ion Nuclei in the Electrolyte Solutions" V.I. CIiizhik, and V.I. MikJUJilov (Page 212) "Computer Simulation of Spin Relaxation in Diluted Lattices" S.K. Misra, and U. Orhun

(Page 214)

"Inhomogeneous Dipolar Broadening and Hyperfine Shifts of Protons Resonance Lines in Solution with Paramagnetic Impurities" E. Belorizky, P. Fries, W. Gorecki, M. Jeannin, P. Maldivi, and E. Goud (Page 21S) "Spin-Lattice Relaxation of 7Lj in Hexagonal and Cubic Li TiS~" W. Kiichkr, P. Heitjans, D. Clausen, A. Payer, and R. SchlJllhom

(Page 217)

"2H and 13C NMR Investigations of Fluorene Single Crystals with Optical Nuclear Polarization" G. BuntkDws1cy, W. Hojfmllnn, and H.M. Vieth (Page 219) "Fast Electron Transfer Kinetics in Photosystem I from Transient EPR-Spectroscopy at Room Temperature" 1. Siec1anann, C.H. Bock, K. Brettel, A.J. van der Est, P. Serif, and D. Stehlik (Page 220) "High Field Nuclear Spin Relaxation in Liquids and Solids"

G. Dieumtmn, and W. SchiTT1lQCher

(Page 222)

"Nuclear Ferromagnetism in KMgF3" P. BOlUlmour, V. Bo'4lfard, C. Fennon, M. Goldman, and J.-F. Jacquinot

(Page 223)

"Chlorine Quadrupole Relaxation in SnCl2·1.S H20.

J. PinuIl, J. Lu:oUk, and Z. Trontelj

(Page 225)

"Numerical Narrowing of EPR Spectra by Differentiation with Smoothing" A.B. Wllckowski

(Page 227)

APPLICAnON Lectures

"A Correlation of the Spin-Lattice Relaxation with the Starch Content in the Grains of a Cereal" R. Degli Agosti, R. Lenk, and H. Greppin (Page 230) Posters "Surface Adsorbed Free Radicals Observed by Positive Muon Avoided Level Crossing Resonance" EmIl Roduner, and I.D. Reid

(Page 232)

"The ESR and ENDOR of Catalytically Active Ti Complexes" Ju. Azilmy, Ju. Bogachn, S. BootIer, V. Volodenko, V. Drapkin, A. Serdyuk, and V. Janchurov

(Page 234)

XVII

"The ESR of Deuterium in Water: The Practical Aspects of the Problem"

A. Grushkin, V. Drapkin, A. Serdyuk, and N. Serebrennikova

(page 236)

"29Si Solid-State NMR Study of the Hydration Products of Tricalcium Silicate in Pastes and Diluted Aqueous Suspensions" R. Rassem, and H. 7Anni-Theveneau (page 238) "The Possibility of Laser Generation in Ferromagnets with Dynamic Frequency Shift"

K. O. Khutsishvili, and S. G. Chkaidze

(page 240)

SUPERCONDUCTORS Symposia Lectures (invited) "NMR Study of Highly Correlated Superconductivity" Y. Kilaoka "NMR-Spin Lattice Relaxation and ESR in High-Tc Materials"

R. Orbach

"Microwave Absorption of Superconductors at Low Magnetic Fields"

K.W. Blazey

(page 244) (page 246) (page 248)

Lectures "Measurement of Surface Magnetic Field of Superconductors by Magnetic Resonance" Y. Maniwa, H. SalO, T. Mituhashi, K. Mizoguchi, I. Shiozald, A. Shinogi, and K. Kume

(page 249)

"Proton Relaxation in the Superconducting Organic Solid (BEDT-TTFhCu(NCSh: Evidence for Relaxation by Localized Paramagnetic Centers" T. Klutz, U. Haeberkn, and D. Schweitzer (page 251) "NQR Study of Cu in YBa2CU3 0 6 95"

M. Kieninger, G. Majer, and A. Seeger

"Magnetic Resonance Below Tc in the Oxygen:.Deficient RBa2Cu30x Superconductors"

A.G. Badalyan, and P.G. Baranov

(page 253) (page 255)

Posters "Spin-Lattice Relaxation, NQR 63Cu and NMR 2osTI, 170 in TI2Ba2ClinClln+l06+2n

(n=0,1,2)" S. V. Verkhovskii, Yu.I. Zhdanov, K.N. Mikhalev, B.A. Aleksashin, V.I. Ozhogin, A.Yu. Yakubovskii, L.D. Shustov, V.P. Tarasov, and V.I. Privalov

"Magnetization Relaxation in HTSC as Studied by Microwave Response"

G.G. lAzarev, D.S. Tipikin, and Ya.S. Lebedev

"Cu NQR-Echo in Superconducting YBa2Cu307_x in Weak External Magnetic Field"

H. Schmiedel, S. Grande, G. Mayer, and B. Lippold

(page 257) (page 259) (page 261)

"On the Influence of Oxygen Deficiency Upon EPR Spectra of TmBa2Cu307-.5"

N. Guskos, Ch. TrikaJinos, S.M. Paraskevas, A. Koufoudakis, C. Mitras, H. Gemari-Seale, D. Niarchos, J. Kuriata, L. Sadlowski, M. Wabia, and F. Lembicz (page 263)

"A Microwave Study of Ceramic High-Tc Superconductors"

1. CiccareUo, M. Guccione, and M. Li Vigni

(page 265)

XVIII

-NMR Investigation of Oxygen-17 in the Bi-Sr-Ca-Cu-o High-Tc SuperconductorsA. Troldner, L. Le Noc, R. Mellet, D. Morin, Y.M. Gao, J. Primot, and J. Schneck

(Page 267)

-Theory of Nuclear Magnetic Relaxation in HTSCsA. Yu. ZavidoI&OY, and M. V. Eremin

(Page 269)

-63Cu Nuclear Magnetic Relaxation in YBaCuOO.N. BtJIcJuun, A. V. Egorov, V. V. Naletov, M.S. Tagirov, and M.A. Teplov

(Page 271)

-Microwave Absorption near To in a Superconducting AI-Oxide Triangular Sierpinski CarpetB. Senning, J.E. D1'U1'fIM11er, P. Erhart, L. Fransioli, P. Martinoli, R. Meyer, and F. Waldner (Page 273) -Decay of Microwave Absorption Signal in High-To Superconductors of ~Cu30 -

P. Erhart, J.E. D1'U1'fIM11er, B. Senning, S. Mini, L. Fransioli, E. Kaldis, S. Rusieck;,

and F. Waldner

(Pace 275)

-La NQR and Relaxation Study of ~Cul_xNi,P4T. Rega, J. Choisnet, F. Borsa, M. Corti, and A. Rigamonti

(Page 277)

- 170

NMR in Oxides and Oxide-Based Ceramics-

T.I. Btutow, and S.N. Stuart

(Page 279)

-Probing Y-Ba-Cu-O Superconductors by Temperature and Pressure Dependent NQR Frequencies1. Mangelschots, H. Zimmermann, H.P. Meister, M. Mali, J. Roos, and D. Brinkmann

(page 280)

-Static and Dynamic ·Electronic Susceptibilities in the Ba2CU40S Superconductor from Knight Shift and Relaxation Measurements(Page 282) H. Zimmemum", 1. Mangelschors, M. Mali, J. Roos, and D. Brinkmann -Magnetic Properties Investigated by EPR and Static Susceptibility in the Superconducting System Yl-xGdxBazCu~o,-&AI. Nicula, A. V. Pop, L. V. Giurgiu, AI. Darabont, and 1. Cosma (Page 284) -EPR Study of Spin Dynamics of Kondo SystemsN.G. FtrtJeyey, and G.l. Mironov

(Page 286)

-NMR Studies of Dilute Magnetic Alloys and SuperconductorsN.G. FarJeyey, and G.l. Mironov

(Page 288)

-Multipolar Interaction Effects in Magnetic Resonance Studies of Conductors and Superconductors N.G. FarJeyey

(Page 290)

-NMR of Rare Isotope 43Ca in HTSC Tl2BazCaCu20sA. Yu. YalcuboYsldi, V.I. Ozhogin, and L.D. Shustov

(Page 292)

-Cu NQR and NMR Relaxation in ~_xSrxCu04M. Corti, F. Borsa, and A. Rigamonti

(Page 293)

-Charge Fluctuations and Superconductivity of Highly Correlated ElectronsA.N. Kocharitm, and P.S. Ovnaian

(Page 295)

- 170,

63CU and 89y NMR Investigation of Spin Fluctuations in High To Superconducting

~Cu306+x-

C. Berthier. Y. Berthier. P. Bulaull. M. Horvaric. and P. Segransan

(Page 297)

XIX

"Nuclear Spin Relaxation in (BEDT-ITF)-Based Organic Superconductors" A. V. Slcripov, and A.P. Stepanov "EPR Detection of the Magnetic Structure in High-Tc Superconductors"

A. Dulcie, B. Rakvin, and M. Pouk

(page 299) (Page 301)

LIQUID CRYSTALS AND POLYMERS Symposia Lectures (invited) "Planar Diffusion, Discrete Jumps and Restricted Diffusion in Columnar Mesophases" Z. Lur., R. Poupko, S. Zamir, S. Alexander, and H. Zimmermann

(Page 304)

"The Rh~NMR Approach to the Viscoelastic Properties of Liquid Crystalline Polymers: MainChain versus Side-Chain Results" A.F. Martins (Page 306) Lectures "Nematic Configuration in Submicron Cylindrical Cavities: 2H NMR Study" G. Crawford, M. VrUan, I. Vilfan, and I. W. Doane

(page 308)

"Theory of Dipolar Relaxation in Lamellar System: Application to Lyotropic Mesophases" J.-P. Koro, 111. Bredel, C. Chochllty, and I.R. C. van tier Maarel (Page 310) "Supercon Fringe-Field NMR Investigation of Diffusion in Molecular Length Scales: Linear Polymers, Networks, and Percolating Clusters of Biopolymer Hydration Shells" W. Unrath, F. Klommler, K. Kontschke, R. Kimmich, and E. Rommel (Page 312) "Diffusion Measurements in Chiral Liquid Crystals" R. Stannarius, and H. Schmiedel

(Page 314)

Posters "CP/MAS NMR Study on Hydrogen-Bonding Interaction and Morphologies of Poly(Vinyl Alcohol) and Poly(Acrylic Acid) Blends and P~ly(Vinyl Alcohol)-Poly(Methacrylic Acid) Complexes Systems" X. Zlumg, K. Takegoshi, and K. HiJdchi (Page 315) "Polymorphic Crystal Structure of Poly(p-Phenylene Sulphide) by IH NMR Method" J. Jurga, I. Kubis, and P. Hruszka

(Page 317)

"2D-Deuteron NMR Studies of Ultraslow Motions in Solid Polymers Phenylflips in the Glassy State and Chain Motions at the Glass Transition" D. Schaefer, M. Hansen, B. Blilmich, and H. W. Spiess (Page 319) "Identification of a Defect Chain Motion in n-Alkanes by Means of NMR Spin-Lattice . Relaxation Time Measurements" E.C. Reynluudt, and I. Basson (page 321) "Collective Order Fluctuations in Liquid Crystals Studied by Transverse Nuclear Spin Relaxation" J. Stohrer, G. GriJbner, C. Mayer, K. Weisz. and G. Kothe

(Page 323)

"Fractal Structure of a Cross-Linked Polymer Resin. A Pulsed Field Gradient, Paramagnetic Relaxation and Small Angle X-Ray Scattering Study" C. Cluu:1uzty. l.-P. Koro. and I.R. C. van tier Maarel (Page 325)

xx "3D 13C MAS NMR Experiment Correlating Order and Dynamics" Y. Yang, A. Hagemeyer, K. Zemke, and H. W. Spiess

(Page 327)

"EPR Study of Free Radicals in Liquid Crystalline Polymers" F. SzJiCI, M. Klimova, Z. Hiouskova, and J. Placek

(Page 329)

"NMR Study of the Polymer Solid Electrolyte PEO(LmF"'>x" J.P. DonoltJ, M.G. Cavalcante, W. Gorecld, C. Benhier, and M. Armand

(Page 331)

"Structure and Dynamics of Discotic Liquid Crystal Polymers" W. Kranig, J. Hirsehinger, C. Boeffel, and H. W. Spiess

(page 333)

"Effect of Translational Diffusion on NMR Spectra of Confined Liquid Crystals" S. KraIj, M. Vilfan, and S. Zumer

(page 335)

"Rotational Viscosity in a Re-entrant Liquid Crystal Mixture - a NMR Study" A.S. Sai1oja, B. Jagadeesh, K. Venu, and V.S.S. Sastry

(Page 337)

"Molecular Dynamics in 40.9 - Proton Spin Relaxation Study" G. RtJvindrruuzth, K. Venu, and V.S.S. Sastry

(Page 339)

"Molecular Orientation Time of Liquid Crystals in Low Magnetic Field"

C.M. Whittaker, S.L. Segel, and D. T. Amm

(Page 341)

"Solid State 13C NMR Study of Macroporous Glycidyl Methacrylate-Ethylene Dimethacrylate Copolymers and of their Derivatives" J. Spevacek, J. StrDktl, and B. Schneider (Page 343) "A Simplified Technique for Analysing Dipolar Couplings of Molecules Oriented in Liquid Crystals" J. Louniltr, M. Ala-Korpela, and J. Joldsaari (Page 345) "NMRIH-NQR14N Cross-Relaxation Spectra in Nematic Ebba" S. V. Dvinlldh, Yu. V. Molchimov, and D. V. Prokopjev

(page 347)

"NMR of Oriented Flexible Molecules" C. Schmidt, M.E. Rosen, S.P. Rucar, D. Caplan, M.F. Quinton, andA. Pines

(Page 348)

"2H-NMR Studies on Uniaxially Drawn UHMW-Polyethylene" H. Decknumn, M. Kunz, and M. MlJller

(Page 350)

"High-Resolution Solid-State 13C NMR Study on Effects of Blending on Chain Dynamics in Polystyrene/Poly (VinyUMethyl Ether) Blends" K. Talcegolhi, and K. Hildehi (Page 351) "Quadrupole Couplings of 83Kr and l3lXe in Liquid-Crystalline Environments" L.P. Ingnum, J. JoIdsOllri, and P. Diehl

(Page 352)

"ESR and ENDOR Studies of Unusually Stable Trapped Electrons in Brominab:d Epoxy Polymer Resins Exposed to UV-Irradiation" J. Kobayashi, and J. Enomoto (Page 354) "D-NMR Study of Microscopic Effects in Collapsing PA Gels" M. Com, L. Pavesi, and A. Rigamonti

(Page 356)

"High Pressure Influence on Processes of Free Radical Stabilization in Irradiated Polymethylmethacrylate Copolymers" S.P. Pivovarov, L.A. Vasilevskaya, and A. Bakhtigereyeva

(Page 358)

XXI

"EPR and ENDOR Study of Semiquinones in Reversed Micelles" D. NietluDnmer, B. Kirsle, and H. Ku"eck "Chain Dynamics of a Liquid Crystal Studied by Proton NMR Relaxation" Marti~, A.M. Giroud-Godquin, and F. Noack

P.J. SebastimJ, A.C. Ribeiro, A.F.

"Proton Relaxation in a Fractal Polymer Chain"

(page 359)

(Page 361)

A. Zidtmsek, R. Bline, G. LaJwjnar, V. Zagar, and A. Bline

(Page 362)

"Hydrogen Bonds and Formation of Dimers in Some Liquid Crystals" A. Zbeliaskova, 1. Zupancic, G. LolUljnar, and A. Derzhanski

(page 364)

"NMR Study of a Ferroelectric Liquid Crystal with Polarization Sign Reversal"

M. Luzar, J. Dolinsek, and R. Bline

(page 366)

"A Model for Correlated Internal Motions and Deuteron Spin Relaxation in Liquid Crystals"

R. Y. Dong

(Page 368)

"NMR Studies of Dynamics in Molecular Crystals"

S.J. Heyes, and Ch.M. Dobson

"Frequency Dependent Selective Relaxation Studies of Deuterons in Liquid Crystals"

K.H. Schweikttt, H. Gotzig, and F. Noack

(page 369) (Page 370)

PHASE TRANSITIONS Symposia Lectures (invited) "Multistability and Chaos in Transverse-Pumped Spin-Wave Instabilities"

H. Benner, F. RlJdelsperger, and G. Wiese

"Hyperchaos in Antiferromagnetic Resonance"

H.R. Moser, P.F. Meier, M. Wanlen, and F. Waldner

(page 374) (page 376)

"Critical Spin Fluctuations and Curie Tempera~res of Ultrathin Ni Films on W(llO): A Magnetic-Resonance Study in UHV" Yi Li, M. Farle, and K. Baberschke (page 378) "Phase Transitions in Acceptor-Graphite Intercalation Compounds: an ESR Study" C. Rettori, S. Rolla, A.M. Gennaro, and G.E. Barberis

(page 380)

Lectures "NMR Lineshape and Relaxation in Incommensurate Systems with Four and Six Components Order Parameters" R. BUnc, and S. Z u m e r ( p a g e 383) "Local and Non-Local Probes in NMR-NQR"

R. Kind, and O. Liechti

"NMRINQR Studies of Phase-Transition Precursors"

J.L. Bjorkstizm

(Page 385) (Page 387)

"14N-NMR Study of the Normal, Incommensurate and Commensurate-Phases of (NH.)2ZnCI4" D. Michel, B. Maller, J. Petersson, A. Trampen, and R. Walisch (Page 389)

XXII

"Fractal Dimensions and Lyapunov Exponents of NMR-Laser Attractors" L. Flepp, R. Holurer, E. Brun, and'Ch. Broens

(Page 391)

Posters "Noise and Coherence in NMR-Laser Dynamics" L. Flepp, R. Holurer, E. Brun, and H.R. Moser

(Page 392)

"NMR-Laser Dynamics Near a Hopf Bifurcation" R. Holzner, and A. W. McCord

(Page 394)

"EPR Evidence for an Intermediate Premartensitic Transition in Pb3(PO.J2" 1. Barbur, S. Simon, I. ArtIelean, and Gh. Cristea

(Page 396)

"Coupling of Rotational Motions at Phase Transitions in Tetrabutylammonium Tetrafluoroborate

(C4~)iNBF4"

B. SZJVranska, A. KoZ/lk, and Z. Pajak

(Page 398)

"Proton NMR Study of the Structural Phase Transitions in Bilayer N-Alkylammonium Chlorides: and CuHpBD3CI" S. Jurga, and A. Wozniak (Page 400)

C;Hl~3CI

"EPR Study of the Phase Fluctuations Near T1 in the Incommensurate (Mg(H20)tJSiF6" R. Hrabansld (Page 402) "Critical Exponent in Normal to Incommensurate Phase Transition in KSC(MoO.J2 by EPR" W. Zapart (Page 404) "39K and 2H NMR Investigation of the Antiferroelectric Transition in KOH and KOD" T.J. Bastow, S.L. Segel, and K.R. Jeffrey

(Page 4(6)

"s'Rb NMR Study of the Glassy Transition in Rbo.68(NDJO.32D2As04" B. Zalar, J. Dolinsek, and R. Blinc

(Page 407)

"NMR Study of Martensitic Transformation in Shape Memory Alloys" S. Rubini, C. Dimitropoulos, and R. Gotthardt

(Page 409)

"Study on the Structural Phase Transition in 1,2,4,5-Tetrachlorobenzene"

C.A. Martin

(Page 411)

NEW METIIODS Lectures "Thermally Detected Electron Spin Resonance of Fe2+ in LiNb03" S. Juppe. and O.P. Schirmer

(Page 414)

"Longitudinally Detected Pulsed ESR Spectroscopy: Low Power Experiments" A. CoUigiani

(page 416)

"Frequency Modulated Oscillators with Soluble Dynamics: A Model for Resonance Spectroscopy" E. van FQQSsen

(Page 418)

XXIII

Posters "Progressive Saturation Relaxation Spectroscopy Method for NMR Investigation of Biological Tissues and Condensed Matter" 1. Pocsik, and P. Paa (Page 420) "Bistability and Stochastic Resonance in Electron Paramagnetic Resonance"

L. Gammaitoni, S. Santucci, M. Giordano, M. MartineUi, and L. Pardi

(Page 422)

"Recent Developments on the Pulsed Field Gradient NMR Technique for Self Diffusion Coefficient Measurements on Various Nuclei" Th. Dippel, K.D. Kreuer, M. Hampele, and A. Rabenau

(Page 424)

"10 and 2D Solid State NMR of Homonuclear Systems Using Magic Angle Spinning"

J.C. Ducluzmp, X. Wu, and K. W. Zilm

(page 426)

"Application of an Inverse Laplace Transform Method to Analysis of Decaying Transients" Y. Balcou (Page 428) "Quadrupolar Echo Train Relaxation of Spin S =312 Nuclei" J.R.C. WIll der Maanl

(page 430)

"Applicability of the LPSVD Technique for the Analysis of High-Resolution Solid-State Carbon13 NMR Spectra of Complex Organic Solids" D. Michel, F. Engelke, and W. KIJIbeI (Page 432) "NMR Parameter Estimation by Proper Model Order Selection" S. Kang, and D. Fiat

(Page 434)

"Magic Angle Spinning NMR Investigations of Molecular Motions and Spin Dynamics in I-Cyanoadamantane" F. Engellu, J. Petersson, and P. Simon (Page 436) "Experimental Aspects of 170 Solid-State NMR Spectroscopy· R. Goc, and D. Fiat

(Page 438)

"Investigation by the Methods of NMR and Angular Correlation of Annihilation Photons (ACAP) of Cyclotron Irradiated Copper" R.K. Zhakparov, A.I. Kolin, S. V. Makarov, and S.P. Pivovarov (Page 440) "A Pulsed ENDOR Probehead with an Operating Frequency Range up to 200 MHz"

J. Forrer, S. Pfenninger, J. Eisenegger, and A. Schweiger

(Page 441)

"Radio Frequency Driven Electron Spin Echo Envelope Modulation" S. Pfenninger, H. aw, J. Forrer, and A. Schweiger

(Page 443)

"Creation and Detection of Nuclear Spin Coherence Using Novel Electron Spin Echo Pulse Sequences" E.J. Hustedt, C. Gemperle, A. Schweiger, and R.R. Ernst (Page 445) "Two New Pulsed EPR Experiments: FT-EPR Detected NMR and FT-Hyperfine-Spectroscopy· (Page 447)

Th. Wacker, A. Schweiger, and R.R. Ernst

·Gaussian Pulse Cascades and Selective Two-Dimensional NMR· L. Emsley, P. Huber, L. Di Bari, and J. Kowalewski ·Wide-Band NMR Spectroscopy with Frequency-Modulated "Chirp" Pulses.·

J.M. BlJhlen, 1. Burgluudt, R. Konrat, M. Rey, and G. Bodenhausen

(Page 449) (Page 451)

XXIV

"Nuclear Quadrupol Resonance Spectrometer" V. lone", Gh. Cristea, I. Barbur, E. Tataru, and S. Simon

(Page 452)

"Deadtime Free Echo Modulation in Pulsed EPR" A. Grupp, Z. S1ummin, and M. Mehring

(Page 454)

"A Fast Field-Cycling NMR Spectrometer" M. Blanz, TJ. Rayner, andJ.A.S. Smith

(Page 456)

"Design and Construction of a 2.4 T Air-Cored Copper Magnet for Fast Field-Cycling NMR" SI. Becker, K.H. SchweiUrt, and F. Noaclc (Page 458) "A MOSFET Transmission-Line High-Power ENDOR Spectrometer" A. Colligiani, and G. Romonenghi

(Page 460)

"A Nonlinear Interferometer for Measurement of ID and 2D Interferograms in NMR and ESR Spectroscopy" J. Paff, B. BlUmich, G. HiJlz., G.G. Maresch, and V. Macho (Page 461) "Simple, Low-Frequency, Short-Recovery Double Coil Probe for Acoustical NMR" F. Floridi, R. Lmnanna, P. Diodati, and S. Cannistraro

(Page 463)

CONDUCTORS AND SEMICONDUCTORS Symposia Lectures (mvited) "Nuclear Spins as Probes for Conduction Electrons" G. Denninger "Near Bandgap Photoemission of Polarized Electrons in Semiconductors"

C. Henrumn, H.-J. Drouhin, and G. Lampel

(Page 466) (Page 468)

Lectures "NMR Studies of Diffusivity and Spin-Lattice Relaxation of Protons and Deuterons in Tantalum" M. Hampele, G. Majer, R. Messer, and A. Seeger (Page 471) "Knight Shift and Diffusion in Solid Lithium and Sodium at Pressures up to 8 GPA Studied by NMR" R. Bertani, M. Mali, J. Roos, and D. Brinkmann (Page 473) "Tunneling and Spin-Lattice Relaxation of Hydrogen Dissolved in Scandium Metal" I. Svare, D.R. Torgeson, and F. Borsa

(Page 475)

"High Resolution 13C NMR Investigation of the Organic Conductor DMTM(TCNQh· F. Raehdi, M. -Ribel, T. Nunes, P. Bernier, and M. Almeida

(Page 476)

"Paramagnetism of Small Metal Particles Studied by NMR" J.-J. Bercier, J.-P. Bucher, Y. Tong, and J.J. van der Klink

(Page 477)

Posters "Anomalous Field Dependence of the Second Moment in Bi Observed by "SR" P. Bi"er, F.N. Gygox, B. Hitti, E. UppelJ, A. Schenck, and M. Weber "Muon Tunneling and Spin Relaxation in Iron"

I. Sva,.,

(Page 479) (Page 481)

xxv "The 14SNd NMR in Magnetic Nd - Co Compounds" H. Figiel, N. Spiridis, Cz. Kapusta, and J. ZuJerowsld

(page 482)

"Pulsed NQR in Metallic Arsenic Under Pressure" J.M. KeaTtland, and M.J.R. Hach

(Page 484)

"Magic Angle Sample Spinning NMR Studies of a Diluted Magnetic Semiconductor Alloy: Cd 1•xMnxTe" D. Zamir, K. Beshah, P. Becla, and R. G. Griffin (Page 486) "Nuclear Magnetic Resonance Study of s7Fe in Zn2Ba2Fe12022 Hexagonal Ferrite"

J. Hanldewicz, and Z. Pajak

"(Z!-Ni)l-~-yPxHLDouble Resonance

G.

LaSIUI.iIa,

in a Glassy Metal" K. lOmpa, A. Werner, and P. Banld

(page 487) (Page 489)

"Spin Resonance of Positive Muons in a-Iron at High Temperatures·

M. Hampele, G. Majer, J. Major, H.P. Raich, R. Roth, A. Seeger, W. Tempi, M. Blanz, K. Filrderer, D. Herlach, A. Kratzer, S.F.J. Cox, and C.A. Scott

(Page 490)

"NMR Characterization of Singlet-Ground State Compound Thulium Dihydride" H. Winter, D. Shaltiel, and E. Dormann

(Page 492)

"Pulsed Field-Gradient (pFG) NMR Study of Self-Diffusion in Liquid Sodium" Th. Pfiz, and A. Seeger

(Page 494)

"Diffusion in Superionic 8-Ag3S1 Studies by Chemical Shift Relaxation"

M. HeTtwig, J. Roos, M. Mali, and D. Brinkmann

(page 496)

"NMR Study of Molecular Dynamics in Some Proton and Organic Conductors" L.N. Ero/eeJ1, Y.G. Shteinberg, and B.A. Shumm

(Page 498)

"(TMTSFh obtained from the noise spectra.

0

o

0.1

0.2 DELAY TIME

0.3

0.4

T(m.)

REFERENCES 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14) 15) 16) 17)

R.E. Peierls, Quantum Theory of Solids, Oxford Univ. Press (1955) H. Frohlich, Proc. Roy. Soc. London, Ser. A22l296 (1954) For a review see "Highly Conducting one Dimensional Solids" ed. J.T. Devreese, Plenum Press, NY (1978) J.A. Wilson, F.J. Disalvo and S. Mahajan, Adv. Phys. 24117 (1974) "Charge Density Wave in Solids", eds. O. Hiitiray and J. Solyom, Lecture Notes in Physics 217 Springer Verlag, Berlin (1985) "Low Dimensional Conductor and Superconductors" eds D. Jerome and L.G. Caron, Plenum Press, NY (1987) D. Jerome and H.J. Schutz, Adv. Phys..ll299 (1982) C. Berthier and P. Segransan, in Ref. 5 J.H. Ross, Z. Wang and c.P. Slichter, Phys. Rev. Lett. ~ 663 (1986) P. Segransan, A. J?mossy, C. Berthier, J. Marcus, P. Butaud, Phys. Rev. Lett. 56 1854 (1986) K. Nomura, K. Kume and M. Sato, 1. Phys. C.l2 L 289 (1986) A. Janossy, C. Berthier, P. Segransan and P. Butaud, Phys. Rev. Lett ~ 2348 (1987) C. Berthier, D. Jerome and P. Molinie, J. Phys. C, Solid State Physics 11 797 (1978) R. Blinc, Phys. Rep.1!J.. 331 (1981) ; R. Blinc, P. Prelovsek, V. Rutar, J. Seliger and S. Zumer, in "Incommensurate Phases in Dielectrics", Eds. R. Blinc and A.P. Levanyuk, Elsevier Science Publishers, B.V. (1986) Chap. 4 P. Butaud, P. Segransan, C. Berthier, J. Dumas and C. Schlenker, Phys. Rev. Lett. ~ 253 (1985) M. Kogoy, S. Zumer and R. Blinc, 1. Phys. i l l 2415 (1984) P. Butaud, P. Segransan, A. Janossy and C. Berthier, J. Phys. France 51, 59 (1990)

7

NMR IMAGING: CURRENT STATUS AND FUTURE PROSPECTS P. Mansfield, R.J. Coxon, D.N. Guilfoyle, A.M. Blamire, P. Gibbs, P. Harvey and M. Symms Department of Physics, University of Nottingham, University Park, Nottingham, U.K. PACS nos. 70.1214, 51.1214 Introduction For magnetic resonance imaging in medicine it is important to be able to image rapidly as well as produce images of high spatial resolution. The speed is important because the body is in general moving. There are roughly three time regimes which are important in determining the imaging speed. The slowest is on a time scale of about 20 seconds and is the time a normal person could reasonably be expected to hold their breath. The second time regime is around 4 or 5 seconds and is the time scale at which peristaltic and intestinal motion occurs. The third and fastest regime is heart motion, and here it is necessary to image at times considerably less than 1 second in order to effectively 'freeze' cardiac motion in time. The historical development of NMR imaging originating with the first papers on the subject in 1973 by Lauterbur, 1) and by Mansfield and Grannell, 2) were concerned with relatively slow imaging techniques. Application and adaptation of these original ideas led to the first wave of commercial machines capab Ie of producing high qual i ty images in 3 to 6 minutes. Such machines have their widest application in static areas of the anatomy, for example the head and pelvis, but even in these regions it is still necessary where possible to speed up the imaging process simply on economic grounds by raising the patient throughput level. Methods and Results The fastest imaging technique yet devised is the so-called echo-planar technique 3) which arose directly from the ideas and principles embodied in the original work referred to above 2). The technique relies upon the observation of a selectively excited free induction decay signal observed in rapidly modulated magnetic field gradients. The rapid modulation of these gradients is technically difficult to achieve and has been the major obstacle in the progress of EPI techniques. Prob lems associated with fast switching include the introduction of slowly varying transient signals in the magnetic structure itself. These kinds of difficulties have been essentially overcome with the availability of new high power gradient amplifiers and the introduction of active magnetic screening by Mansfield and Chapman, 4). Echo-planar techniques as the name implies are concerned with imaging in a single slice or plane, an9 high resolution snap-shot images can be produced in times as short as 60 ms with current spatial resolution of 3 x 1.5 mm 2 . In our own homebuilt imaging system the magnetic field strength is 0.5 T.

8

Results from EPI and from the slower FLASH imaging methods 5) will be discussed. Future

P~ospects

and Conclusions

EPI techniques can be successfully combined with spectroscopic imaging to produce images and spectra in a single snap-shot. However, these techniques are really only likely to find application at much higher magnetic field strengths where one can observe spectra in vivo for nuclei other than protons. Another new and potentially exciting ultra fast imaging technique is echo-volumar imaging (EVI) 6). The technical demands on apparatus are even greater for this technique, but it is nevertheless possible to obtain complete three-dimensional images in a snap-shot imaging time of 128 ms. Current spatial resolution is not _as good as EPI, but the ability to look at a complete volume rather than a plane could have important clinical consequences when studying for example the heart which moves in three dimens ions. EVI can also be valuable in studying the bowel. The inherently random peristal tic motion in the gut could make it difficul t to get good plane-to-plane correlation from successive scans. EVI, on the other hand, is able to get a complete description of the object field independently of motion. The principles of BPI and related techniques introduced using the k-space description 2,7).

will

be

Acknowledgments We are grateful to the Medical Research Council, the Department of Health and the British Heart Foundation for major support of the echo-planar imaging programme. References 1.

2. 3. 4. 5. 6. 7.

P.C. Lauterbur, Nature 242, 190, (1973). P. Mansfield and P.K. Grannell, J. Phys. C. 6, L422 (1973). P. Mansfield, J. Phys. C. 10, L55 (1977). P. Mansfield and B. Chapman, J. Phys. E. 19, 540 (1986). A. Haase, D. Matthaei and D. Norris, Proc. 8th Ann. Mtg. SMRM Amsterdam I, 304 (1989). P. Mansfield, A.M. Howseman and R.J. Ordidge, J. Phys. E. 22, 324 (1989). S. Ljunggren, J. Mag. Res. 54, 338 (1983).

9

ESR-EXPERZHEHTS ON THE TWO-DZHENSZONAL ELECTRON GAS OF BETEROSTRUCTURES

K. von Klitzing, M. Dobers, A. Berg Max-Planck-Institut fur Festkorperforschung, Heisenbergstr. 1 7000 stuttgart 80, Fed. Rep. of Germany PACS number: 72.20.My, 72.80.Ey, 76.30.Pk, 76.60.Es ZHTRODUCTZON

The epi taxial growth of thin layers of semiconductors, where the composition of the material can be changed within one lattice constant, is used for the realization of new microelectronic devices. The simplest structure consists of an interface between the semiconductors GaAs and AlGaAs. Free electrons are present at the GaAs-side of the interface if the AlGaAs material is doped with donors. Calculations show that the electrons are confined within a narrow interface region of about 10 nm which leads to a quantization of the energy within this channel (electric subbands). In our experiments only the lowest electric subband EO of such a two-dimensional electron gas is occupied with electrons so that the energy is the sum of the fixed energy EO for the motion perpendicular to the interface and the free motion within the plane. A strong magnetic field B perpendicular to the interface leads to an additional quantization (Landau quantization) resulting in a discrete energy spectrum for the conduction electrons: E =

EO+(n+1/2)hWc±g~BB

n 0,1,2 .•• Landau quantum number Wc = cyclotron frequency g = electronic g-factor The strong variation of the density of states at the Fermi energy as a function of the magnetic field leads to Shubnikovde Haas oscillations in the magnetoresistance with minima if the Fermi energy is located in gaps between the discrete energy levels. Fig. 1 shows a typical result. The filling factors i=3,4,6 determine the number of fully occupied energy levels and are defined as the ratio between the carrier densi ty n and the degeneracy n L=h/ (e B) of each level: i=nS/nL • ~he filling factor i=3 characterizes the situation where the Fermi energy is located in the gap between the spin split levels of the Landau level n=1. Under this condition, the ESR signal can be observed directly as a change in the resistivity (see Fig. 1). This method allows the detection ~O the electron spin resonance even in a system with only 10 electrons where conventional absorption measurements are not sensitive enough. The resonance energy has been measured systematically as a function of the Landau level index n for different samples with different subband energies Eo' In addition the Overhauser shift has been studied which gives information about the nuclear spin lattice relaxation process.

10

1.3K

23.07 GHz ..,.32.6°

.

Q.

-ESR 3

4

BIT!

5

6

7

8

FIG. 1. Magnetoresistivity of a two-dimensional electron gas of T=1.3 K under microwave radiation of 23.07 GHz. The small peak around 5.5 Tesla shifts with the microwave frequency and is connected with ESR. The filling factor i=3,4 and 6 determines some magnetic field positions where an integer number of Landau levels is occupied.

RESULTS

Measurements of the ESR frequency as a function of the magnetic field show, that the g-factor of 2D-electrons in GaAs depends on the electric subband energy EO' the magnetic field B and the Landau level index n g = go(E o )-a(n+1/2)B Typical values for the parameter go and a are I go I =0.41 and a=O.012 Tesla- 1 . The measurements agree with calculations which demonstrate that mainly the nonparabolicity of the GaAsconduction band leads to the observed variations of the gfactor. contrary to 3-dimensional systems, the Fermi energy relative to the conduction band minimum can be changed by more than 20 meV in a two-dimensional system without changing the sample so that systematic studies of the nonparabolic bandstructure is possible. The magnetic field position of the ESR-signal is influenced by the ~erfigg inteffction with the spins of the lattice nuclei (As, Ga, Ga). Such Overhauser-shift becomes visible if the nuclear spin polarization (which is negligibly small under thermodynamic equilibium) is dynamically enhanced as a result of the relaxation of excited electrons in ESR experiments. Overhauser shifts up to ~~0.5 T are observed and the relaxation of this shift with a time constant up to 1000 sec has been analyzed in order to get information about the nuclear spin lattice relaxation rate 1/Tl. It is found that this relaxation rate is connected with the density of states of the electronic spin levels at the Fermi energy. Experimental results are summarized in Fig. 2 together with model calculations based on the assumption that the Korringa relaxation is the dominating nuclear spin lattice relaxation process. The oscillatory behaviour of the relaxation rate as a function of the magnetic field, which is in phase with the electrical resistivity, demonstrates that the interaction with the two-dimensional electron gas dominates the nuclear spin lattice relaxation.

11

III .....

'2

::J

.D

.... .£ )( )(

Q.

,.

,....,III I

S2

5

6

7

B (Tl

8

9

FIG. 2. Comparison between the oscillations in the magnetoresistivity Pxx and the nuclear spin latt1ce relaxation ratel/T 1

12

MUON SPIN ROTATION EXPERIMENTS IN SOLIDS H. Keller Physik-Institut der Universitat ZUrich, Schonberggasse 9 CH-8001 ZUrich, Switzerland.

ABSTRACT A short overview of the basic principles of the muon spin rotation (JLSR) technique and its potential applications to some selected problems of solid state physics is presented. PACS number: 76.7S.+i INTRODUCTION The new generation of high-intensity intermediate-energy accelerators has made it possible to use the positively charged muon adua, Italy b Department of Inorganic Chemistry and Molecular Structure, University of Messina, Salita Sperone 31, 98100 Messina, Italy PACS number: 76.30.-v

ABSTRACT. - The TCNQ triplet trap in the Biphenyl(B)-TCNQ crystal host and of the triplet exciton of the Phenazine-TCNQ crystal is studied by time resolved EPR spectroscopy. Spin relaxation and decay times are determined and the spectral features are discussed. INTRODUCTION The strong electron-acceptor tetracyanoquinodimethane (TCNQ) forms chargetransfer (CT) complexes with various donors. Although there is much information on the ground state and on the first excited singlet state, little is known about the first excited triplet state of the molecule. EPR and ODMR studies have been carried out recently on CT crystals containing TCNQ as a guest molecule in host crystals [1] as well as on pure crystals [2] . Here, we present the results of a time-resolved EPR study [3] of the TCNQ triplet trap in the B-TCNB crystal host and of the triplet exciton of the Ph - TCNQ crystal. RESULTS AND DISCUSSION The CT crystals illuminated by a laser pulse inside the microwave cavity of an EPR spectrometer give rise to EPR signals due to excited triplet states. The time evolution of the EPR signals in the B-TCNQ triplet is shown in Fig. 1 . O.SmW

A

B 230K

Fig. 1

--30,..

The emissive A and absorptive B lines maintain their initial polarization even at long times. Such a behaviour is explained by assuming spin selection in the

25

decay from the triplet sublevels. From simulation of the signals recorded at different values of microwave power P relaxation times T 1 and T 2 and triplet lifetime T have been determined. At 230K and Bol Ix (long in-plane axis of TCNQ) we obtain T2 = 2.5 ± O.lJLs, Tl = 14 ± 1JLs and T = 80 ± 5JLs. EPR transient signals of the Ph-TCNQ triplet exciton have been studied as a function of P to determine spin relaxation times. In Fig. 2 we report signals monitored with Bollz ( axis normal to the TCNQ molecular plane) for the low (A) and high (B) field transitions (at 280 K and P = 100 mW)

A

Fig. 2

B

_ "'----

They result from the superposition of two signals with reversed initial spin polarizations. The measured values of T 1 for them are 1JLs and 1.5JLs rather independent of crystal orientation. The possible processes giving rise to the observed spectral features are discussed.

REFERENCES 1) L. Pasimeni, C. Corvaja, G. Agostini and G. Giacometti, Chem. Phys. 97 (1985) 357. 2) D. Gundel, J. Frick, J. Kr~ystek, H. Sixl, J. U. von Schlitz. and H. C. Wolf, Chem. Phys. 132 (1989) 363. 3) R. Furrer, F. Fujara, C. Lange, D. Stehlik, H. M. Vieth and W. Vollmann, Chem. Phys. Lett. 75 (1980) 332.

26

HIGH-SPIN MULTIPLET ENOOR AND TRIPLE RESONANCE: ITS APPLICATION TO A MODEL COMPOUND FOR ORGANIC FERRlMAGNEIS T. Takui, M. Endoh, S. Kita, Y. Teki, T. Kinoshita, K. Itoh Department of Chemistry, Faculty of Science, Osaka City University Sugimoto -3-3-138, Sumiyoshi-ku, Osaka 558, JAPAN ABSTRACT We have applied single-crystal ENDOR and TRIPLE resonance spectroscopies to the first organic high-spin molecule, m-phenylenebis(phenylmethylene), 1 in its quintet ground state, establishing high-spin multiplet ENDOR and TRIPLE resonance spectroscopies. Both the magnitude and absolute sign of alii the proton hyperfine coupling constants have been determined from the H-ENDOR/TRIPLE data, yielding crucial information on the spindensity distribution in its pi-electron network. We have designed and synthesized a model compound, 2 for the units of organic ferrimagnets which possesses lantiferrgmagnetically-exchange coupled heterospins. The high-spin multiplet H-(or C-) ENDOR and TRIPLE . resonance of the heterospin system have demonstrated the -salient features of its spin structure which can be characterized in terms of unusually large negative spin polarization.

fP fP fP ~I ~ r I O~I ~I ~I ~~~ 9'

9'

INTRODUCTION 1 • 2 • • The quest for organic magnetism is the focus of current topics in many fields of both pure and applied science I). Organic high-spin molecules have accepted increasing interest as models for synthetic organo-magnetic or molecular based magnetic materials such as organic superpara-, ferro-, and ferri-magnets. Our strategy for obtaining organic magnetism contains both molecular design for high-spin assemblies exploiting topologically-degenerate pi non-bonding MO's and the criteria of the spin alignment between the high-spin assemblies via functional bridges or spacers 2). As part of our project for organic magnetism and spin ordering in chemistry, we have applied single-crystal ENDOR and TRIPLE (electron-nuclear-nuclear-TRIPLE resonance) spectroscopies to the first organiC high-spin molecule, I in its quintet state 3), demonstrating the features of high-spin mUltiplet ENDOR and TRIPLE resonance. This paper also describes an application of highspin multiplet ENDOR/TRIPLE resonance to a novel organo-magnetic molecule 2. RESULTS AND DISCUSSION The high-spin molecules adopted here were formed by the photolysis of corresponding diazo precursors. Single crystals of benzophenone-d 10 containing the corresponding diazo precursor were prepared and irradiated at 4.2K with a 500W high-pressure mercury lamp. ENDOR/TRIPLE measurements were made on both a home-made X-band spectrometer and a Brucker ESP350 spectrometer with a home-made RF irradiation coil and an Oxford 9\0 variable temperature controller. Figs.l(a) and l(b) show, respectively, the H-ENDOR and TRIPLE spectra of 1 observed when the I Ms=+O> ~--l>- I Ms=+ 1> ESR transition was monitored. The figures in Fig.l denote the positions of fourteen protons belonging to 1. The lines labeled by the figures were attributed to the ENDOR transitions assigned to the Ms=+1 manifold, while most of the unlabeled lines were attributable to the Ms=O manifold. The Ms-assignment straightforwardly reveals that the ENDOR spectrum comprises five protons with positive hfcc's and nine protons with negative hfcc's. The polarity of the TRIPLE signal exclusively determined the Ms-assignment of the ENDOR transitions, viz., the absolute sign of the hfcc's, as shown in Fig.l(b), where the V N+ line was the observer. The TRIPLE transitions belonging to the same Ms-manifold (Ms=O in Fig.l(b)) as that of the observer diminish

27

their intensities, while those belonging to the other Ms-manifold (Ms=+ I in Fig. I(b)) increase their intensities. The pi-spin density distribution on the carbon atoms of I obtained from the experimentally determined isotropic hfcc's was compared with the results from the simple MO and a generalized Hubbard model calculation 4). The INDO calculation reproduced the observed hfcc's, predicting the most probable non-planar molecular structure for 1. We have designed and syn~ ~ ~ thesized a prototype of org- ..IENDOR ~ anic ferrimagnetic molecules, • r 2,4T4'Q-ether. 4T4'Q-ether is the first example of the organo-magnetic molecules with antiferromagnetically-exchange coupled heterospins. In the 7' 7 11'9' 911 3' case of 4T4'Q-ether, the triplet spin moiety is predicted to possess large negative pispin distribution. Fig.2 shows a typical H-ENDOR spectrum of partially deuterated 4T4'Qether in its magnetic ground state (S=1). Since the I Ms=15 30141> 20 25 I> I Ms=O> ESR transition was ,monitored, the ~ignal~ ap- Fig.1 IH-ENDOR and TRIPLE spectra of 1 in a peanng at frequencies higher benzophenone-d crystal with H II b axis at 4.2K 10 . than the free proton NMR freD . D quency VN were assigned to the I M.=-J> - I M. = 0 > D("yD t"""'l f " ' Y 0 0 ; 0 0 protons of positive hfcc , s, pumped .I~ ~ viz., to the negative pi-spin 0 D·· If· D 0 densities on the carbons bond- V".20.7742MIIz If ed to the corresponding proIf It tons. Thus, the five lines marked by the as-terisk arise from the negative pi-spin densities. The complete ENDOR /TRIPLE analysis showed that their absolute values nearly amounted to half of the positive ones of the , constituent triplet dipheP,1.lI~.' I' , I lO.O methylene. The results of CI.D ll.O l6.0 ' I b 't 1 FltEQUENCY IMlIz • I a b e Ie,d d Iva ent car on Sl es Fig. 2 H-ENDOR spectrum of 4T4'Q-ether in a of 2 wIll be also presented. benzophenone-d crystal with H II . t 3K CONCLUSIONS 10 a BUS a • We have established high-spin multiplet ENDOR and TRIPLE resonance spectronscopies, showing that they give crucial information on the pielectron network of high-spin molecules. The high-spin multiplet ENDOR and TRIPLE resonance have been applied to an organic ferrimagnetic molecule, demonstrating that unusually large negative spin polarization is characterist ic of such a heterospin ferrimagnetic system and providing a usable physical picture for the understanding of organic ferrimagnetism. REFERENCES 1) "Ferromagnetic and High Spin Molecular Based Materials", 197th ACS Meeting (Dallas) (1989): Mol. Cryst. Liq. Cryst., 176 (1989). 2) K.Itoh, T.Takui, Y.Teki, T.Kinoshita, J.Mol.Electronics, 4, 181(1988). 3) K. Itoh, Chern. Phys. Letters, 1, 235 (1967). 4) Y.Teki, T.Takui, T.Kinoshita, S.Ichikawa, K.Itoh, ibid., 141, 201(1987).

28

mCAL DEFORMATION AND HYPERFINEFIELDS ON THE LIGANDS IN TRI GONAL CENTRE Yb 3+ IN KMgF3

M.V.Eremin, M.M.Zaripov, I.R.Ibragimov, M.P.Rodionova, M.L.Falin Physico-Technikal Institute, Kazan branch of the Academy of Sciences of the USSR, Kazan Abstract. The experimental investigation of transferred hyperfine interaction (THFI) of the trigonal centre Yb 3+ with F- ions of the nearest enviroment in KMgF3 crystal was carried out by means of ENOOR. The theoretical analysis of THFI parameters was based on the calculation of the deformation of the crystal lattice of KMgF3 •

Recently new concepts about the interaction between impurity paramagnetic ion in dielectric crystals and nuclear moments of ligands fOI'ming the nearest environment (THFI) were developed in l11 • They enabled to explain not only the variety of exper;mental data for impurity rare-earth ions in fiuorides with cubic local symmetry but also some experimental THFI parameters for impurity centres (IC) haviilg local symmetry lower than cubic one (CaF 2 : Ce3+, Tb 3+) for the first time [2,3J • The local deformation model was known for different IC types in fluorite crystals (CaF 2) [4] , thus determining the successful results of the works l2,31 • The attempts to apply new THFI theory to low s~~etry IC in crystals with a structure differing from that of fluorite were hampered by the absense of corresponding local deformation models of these centres. The present work is concerned with the experimental results and theoretical investigation of THFI of trigonal Yb 3+ in perovskite-type crystals (IDdgF3). The present investigation shows that the nearest environment of Yb 3+ is an octahedron of 6 fluorine ions, formed

29

by two nonequivalent groups of F-. An extra positive charge of Yb 3+ is compensated due to the vacancy at the site of a nearest K+ ion. THFI parameters of Yb 3+ with F- ions from the nearest environment are det ermined. For the theoretical THFI analysis a microscopic calculation of the deformation of the crystal lattice of El~3 near the IC was carried out. The values of displacement and induced dipole moments Vlere calculated using minimum condition for the bond energy of the crystal. The displacement of five coordinational spheres, formed by F-, K+ and Mg2+ ions Vias taken into account. Calculation of the local deformation enables to obtain IC model Yb 3+ and a qualitative evaluation of interion distances. The THFI calculation allows for the mechanism of spin polarization of external filled 5s, 5p-shells of Yb 3+ together with mechanisms suggested in [1,2J • The obtained results were discussed. References 1) Anikeenok 0 A, Eremin M V, Falin M L, Konkin A L and Meiklyar V P 1984 JoPhys.C: Solid State Phys. 11 2813 2) Anikeenok 0 A, Eremin M V and Khytsishvili 0 G 1986 Fiz.TverdoTela ~ 1690 3) Eremin M V and Falin M L 1987 Fiz.Tverd.Tela ~ 591 4) Davydova M P, Malkin B Z and Stolov A L1978 Spektroskopija Kristallow (Moscow: -Hauka)

30

SPXN-LATTXCE RELAXATXON OF F+-CENTERS XN NEUTRON XRRADXATED CaO CRYSTALS G. Liidja, T. Room Institute of Chemical Physics and Biophysics, Estonian Academy of Sciences, Lenini puiestee 10, 200001 Tallinn, Estonia, USSR ABSTRACT We have measured the spin-lattice relaxation rates of F+centers at different F+-center concentration in magnetic fields from 10-3 T to 4.8 T and at O. 4K < T < 4. 2K. The intrinsic KronigVan Vleck spin-lattice relaxation mechanism was not found. At higher temperatures the relaxation rates are nearly proportional to the F+-center concentrations. PACS numbers: 76.30.Mi, 76.70.Hb XNTRODUC't:tON F+-center is a simple defect with one electron in 0 2- vacancy. Calcium and oxygen nuclear spins are zero and the only one expected intrinsic spin-lattice relaxation mechanism is the Kronig-Van Vleck mechanism. It was found [1] that the F+-centers spin-lattice relaxation rate depends on crystal treatment. EXPERXHENT We have measured the recovery of the equilibrium value of spin magnetization of the F+ centers after rapid changes of the log

T

-1

,

s

---.----r---

-1

I

..... ,0,6~_31

T = 2K

o 3.10 16 cm- 3

0

0

I I

~

•

-1

T = O.4K

i

•

-2

~ I I I

·~o .0

i

I

! -3

-3

-2

-1

Fig. 1

0

log B, T

31

log 1:

-1

, S

-1

o

• 6.a.l0 16 cm- 3 o 3.10 16 cm- 3

-1

mag?etic field B, uSl.ng magnetic circular dichroism in the F+ absorption band as a detection method (see, e. g • [2]). F+centers concentration in the crystal was 6,8'10 16 cm- 3 after irradiation with fast neutrons (1. 7 -10 17 n.v.t.) and 3'10 16 cm-3 after subsequent thermal treatment. RESULTS

Although the signal recovery had usually a complicated time dependence, we used . a single exponential approximation. The field -3 4 dependence (fig. 1) 2 1 0.3 o.S was slower than r -1,., T,K ,.., B- 1 • A power dependence on temperature Fig. 2 (fig. 2), 1"-1,., with 1.7 < x < 2.2, appeared at T > 1 and levelled off at the lowest temperature. At T ~ 2K relaxation rates are nearly proportional to the F+-center concentration, whereas at T = 0.4K they are independent of concentration. -2

r

DISCUSSION AND CONCLUSIONS

An intrinsic Kronig-van Vleck relaxation having ~rate dependence of r -1 ,., BS coth (g,BB/2kT) was not found at least below 4.8 T. We propose that relaxation goes through some fast relaxing centers having energy splitting independent of field (e.g. exchange coupled F+-center pairs [3] or hydrogen related [ 4 ] tunneling centers). At T > 1K spin diffusion between F+ centers may have some importance. Existing theories of relaxation through tunneling states [5] or exchange coupled pairs [6] do not fit our experimental results.

1. J.C.Kemp, V.M.Ziniker, J.A.Glaze, Proc. British Ceramic Soc. (1967), v. 9, p. 109-123. 2. V.S.Zapasskii, P.P.Feofilov, Usp. fiz. nauk (1975), v .• 116, No.1, p. 41-78. 3. B.Henderson, J.E.Wertz, Defects in the Alkaline Earth Oxides, London 1977, p. 105-108. 4. V.M.Orera, Y.Chen, Phys. Rev. B (1987), v. 36, No.2, p. 12441247. 5. D.G.Stinson, H.I.Stapleton, Phys. Rev. B (1983), v. 27, p. 5386-5393. 6. I.M.Zaritskii, Y.G.Semenov, Fiz. tehn. poluprov. (1988), v. 22, No.3, p. 402-407.

32

ESR-INVESTIGATIONS ON THE SOLID SOLUTION M9 2 _ x Cu x P 4012 W. GunOer, A. Zimmermann Univ.rsitit Hamburg, Institut fUr Physikalische Chemie, BundesstraOe 45, 2000 Hamburg 13 ABSTRACT ESR-investigations w.re performed on the solid solution M9 2 _ x Cu x P 4012' Th. single ion spectrum shows a tetragonal g-tensor which is caused by a planar-quadratic dynamic Jahn-Teller effect. At 2 K a HFS is observed. Pur. Cu 2 P 4012 exhibits a static Jahn-Teller-distortion even at room temperature. The onset of ferrimagnetic ordering below 8 K leads to a pronounced shift of the g-values.

INTRODUCTION Copper (l1)-cyclo-tetraphosphate Cu 2 P 4012 is a member of the isomorphous group of cyclo-t.traphosphates M2 P 4012 (M 2 + Mg, Mn, Fe, Co, Ni, Cu). They crystallize in the monoclinic space group C2/c. The metal ions are octahedrally coordinated by exocyclic oxygens of thecyclo-tetraphosphate anions. In the copper compound the octahedra are distinctly distorted, due to the Jahn-Teller effect. The octahedra share edges to form zigzag chains of' cations, which are separated by layers of anions. Magnetic quasi-one-dimensional behavior has been established for manganese-cyc!otetraphosphate [1]. Copper-cyc/o-tetraphosphate shows a ferrimagnetic long-range order (LRO) below 8 K. Static magnetic measurements also indicate ferrimagnetic one-dimensional short-range order below 15 K. We obtained homogenous phases of the solid solution M9 2 _ x Cu x P 4012 in the concentration range of 0 80 K in the glass samples. The EPR signal intensity of the sample without Gd203 gradually decreases with the heat treatment time and practically disappears after heat treatments longer than 10 hours. The shape of the EPR spectra for samples containing Gd203 modifies with the increase of the crystallization degree of the samples. One remarks

83

__---x=O

a share diminution for the signals with ge~6.0 and a broadening of the line with geff=2.0 respectively. The same behaviour was also observed 3) for other glasses doped with Gd~+.

CONCLUSIONS Having in view the assignement of the resonance x=O.OS line with geff> 2.0 from the EPR spectra of Gd3+ ions in glasses 5,6) one may assert that in the investigated samples oUly a small part of the Gd?+ x=O.1O ions are disposed in sites of low symmetry and that the most ones occupy sites x=O.1S of cubic symmetry with minor axial components. By x=O.30 the partial crystallization of the glasses it takes place a relaxation of the I .. sites of low symmetry. At 26OO(6J the same time the microenvironments of the Gd?+ions disposed in sites of cubic symmetry are aesily distorFig.l ted, what involves a broadening of the distribution range of the values corresponding to the axial symmetry crystalline parameters. This leads to broadening of the line with geff=2.0. To this broadening also cQntributes the increasing magnetic interaction between the Gd?+ ions. Because the fine structure of the Gd3+ EPR spectra from partially crystallized samples is not resolved, it is difficult to specify the sites in which these ions are disposed relatively to other component elements. REFERENCES 1) T.Komatsu, K.Imai, R.Sato, K.Matusita, J.Yamashita, Jpn. J. Appl. Phys., 27, L 533 (1988). 2) Y.Y.Xue, P.H.Hor, Y.Y.Sun, Z.J.Huang, L.Gao, R.L.Meng, C.W.Chu, J.C.Ho, C.Y.Wu, Physica C, 158, 1-2, 211 (1989). 3) S.Simon, Gh.Ilonca, I.Barbur, I.Ardelean, R.Redac, Physica C, 162-164, 1289 (1989). 4) S.Simon, Al.Nicula, Solid st. Commun., 39, 1251 (1981). 5) R.C.Nicklin, Y.K.Johnstone, R.C.Barnes, R.Wilder, J. Chem. Phys., 59, 1652 (1973). 6) C.M.Brodberk, L.E.lton, J. Chem. Phys., 83, 9, 4285 (1985).

84

THE VALENCE STATES AND INTERACTION BETWEEN CHROMIUM IONS IN LITHIUM-BORATE GLASSES O.Cozar,I.Ardelean, Gh.Ilonca, S.Simon, I.Barbur, I.BratuI Un~versity of Cluj,Department of Physics, 3400 Cluj, Romania I Institute of Isotopic and Molecular Technology, 3400 Cluj, Romania ABSTRACT The valence states and interaction between chromium ions in xCr203(1-x) [2B203.Li20J glasses with 0.5 (,.X ~ 20 mol % Cr203 were studied by EPR and magnetic susceptibility measurements. EPR spectra indicate the presence of both Cr?+ and Cr5+ ions. For concentrations x ~ 3 mol % Cr203 the isolated Cr 3+ ions coexist with those coupled by dipole-dipole or super-exchange interactions. PACS number: 76.30.F INTRODUCTION EPR and optical studies on phosphate glasses with Cr203 suggest only the presence of Cr3+ ions 1,2). Two absorption peaks at g~5 and g~1.97 have been evidenced. The spectrum at law field was assigned to isolated Cr 3+ ions and that at high field (g=: 2) to exchange-coupled cr 3+ pairs. In sodium borate glasses 3) only a g ~ 2 resonance was observed, the shape of which is dependent on the alkali content. The absence of higher g resonance implies that the zero-field splitting of the observed chromium centre is considerably smaller in borate than in the phosphate glasses. On the other hand, EPR investigation of xCr203(1-x) [3B203-PbO] glasses 4) had evidenced the presence of both cr 3+ and Cr5+ ions. In order to obtain further information on the chromium valence states and its distribution mode in oxide glasses, we have studied the xCr203(1-x) [2B203·Li20] system with 0.5 ~ x,20 mol % Cr203. The EPR measurements were performed at 9.4 GHz (X band), using a standard JEOL-JES-3B equipment at the 295 K. RESULTS AND DISCUSSION EPR spectra of xCr203(1-x)[2B203.Li20J glasses are shown in Fig.l. These indicate the presence of both cr 3+ and cr 5+ ions in the studied glasses. The Cr 5+ ions are characterized by the narrow signal (tlBl =: 45 Gs) from g = 1.975 and cr 3+ ions by the broad low-field absorption, g::: 5.1 4,5). This resonance absorption is typical for isolated Cr 3+ ion sites of rhombic symmetry subjected to strong crystal field effects 1). The resonance absorption having g = 1.975 results from contributions of both cr 5+ and Cr 3+ ions. We notice that for glasses containing 0.5 to 1 mol % Cr203 the predominant contribution to g~ 1.97 resonance is due to the Cr 5+ ions. The Cr 3+/Cr5+ ratio and thus the shape spectra are strongly dependent on the Cr203 content. As the Cr203 concentration increases (x ~ 3 mol ~) a broad resonance line (AB2 =: 350 Gs) due to the coupled Cr3+ ions is

85

superposed upon the narrow one due to Cr5+ ions. The prevalent coupling interaction between Cr3+ ions is that of the dipole-dipole type for glasses with 3~x ~10 mol %. The number of coupled Cr 3+ions increases with Cr203 content and for x> 10 mol % the superexchange interaction prevails. Thus,the characteristic line width of coupled Cr3+ pairs decreases at 315 Gs for x=20 mol % Cr203' The magnetic susceptibility measurements show also that in glasses with x ~ 10 mol % Cr203 the chromium ions unaergo negative exchange interactions and are coupled antiferromagnetically. From Fig.l Curie constant and atomic magnetic moment values we have established the presence and ratio of both Cr'+ and Cr 5+ ions in these glasses. CONCLUSIONS The EPR studies sho\Y' that in these glasses both cr 3+ and Cr5+ ions are present. These data correlated to magnetic susceptibility studies indicate that cr 3+ ions coexist simultaneously in two states, as isolated ions and coupled pairs by superexchange interaction. The isolated Cr3+ ions prevail at concentration less than 3 mol % Cr203, giving rise to the absorption centered at g =- 5.1. Apart from this, for concentrations x < 3 mol % Cr203' there is another narrow signal at g:! 1.975 due to Cr5+ ions. With increasing of Cr203 concentration, a broad resonance absorption characteristic. for coupled Cr3+ ions superimposes at g=-1.97 on the signal due to Cr 5+ ions. REFERENCES 1) R.J.Landry, J.T.Fournier, C.G.Young, J.Chem.Phys.,46, 1285 (1967). 2) O.Cozar, I.Ardelean, Gh.Ilonca, T.Fiat, L.Pasca, in vol. "Lucrarile celui de al III-lea Colocviu National de Fizica si Tehnologia Materialelor Cristaline si Amorfe", Iasi, 1988, p.40. 3) D.Loveridge, S.Parke, Phys. Chem.Glasses, 12, 19 (1971). 4) I.Ardelean, Gh.Ilonca, M.Peteanu, E.Barbos, E.lndrea, J. Mater. Sci., 17, 1988 (1982). 5) E.Trif, D.Strugaru, I.Ivan, R.Russu, G.Gheorghe, in vol. "Probleme actuale de fizica", Univ. Cluj-Napoca, 1988, p.23.

86

Results of high-field 31P-NMR investigations of crystalline and amorphous phosphate systems with increased spectral resolution B. Schnabel. P. Hartmann. P. losso Department of Physics, Friedrich-Schiller-University, Jena Following the work of Haubenrei8er Ill, four types of phosphate groups can be definitely identified in phosphate systems. This is due to we1lseparated ranges of the ~lP-NMR magnetic shielding tensor anisotropy reflecting the different spatial symmetry properties of these different structural units. These groups are: monophosphate groups (Q"'), diphosphate groups (Ql), chain phosphate grotlps (Q::!) and branching phosphate groups (Q"). Moreover, a linear correlation c·ould be found of the isotropic value of the 31P-NMR magnetic shilding tensor and the Dietzel field strength of the elements forming part of the secound coordination sphere of the phosphortls. Recently, further effects in crystalline and amorphous phosphate systems have been found. 1. E-,2 = 4>3 = 7r/4. For imaging purposes, the pulse phases must be altematingly in-phase and orthogonal to the first pulse in order to obtain the full information (1). This three-pulse sequence in general implies variable flip angles, pulse phases and delays which must be optimized. It is therefore desirable to carry out analytic model calculations. For simplicity, one considers two-spin (1/2) systems. Model calculations have been carried out using the general density matrix formalism as well as a product operator formalism for strong spin-spin coupling (3) which has been adapted to the problem. All non-secular terms of dipolar coupling have been neglected. In order to get analytical expressions as results, we have employed computer algebra (MUMATH). Both treatments lead to identical results permitting the derivation of the optimum parameters of the pulse sequence.

TEST EXPERIMENTS Both imaging and localized spectroscopy have been tested by the aid of a research tomograph (Bruker BMT 47/40). Phantom samples approaching the prerequisites of the the theoretical treatment have been prepared. As a first step towards an application in materials science, the orientation in Kevlar/wax fibre bundles has been deduced from the local wide-line spectrum and imaged.

CONCLUSIONS The predominant aim of solid-state NMR imaging and localized spectroscopy is neither the representation of spin densities alone nor an extreme spatial resolution. One rather has the unique possibility to image local molecular properties derived from wide-line spectra and relaxation times. This type of information is inaccessible with NMR line-narrowing or even optical techniques. Model calculations with two-spin systems are possible by the aid of a product operator formalism. The Jeener-Broekaert version of the three-pulse phase-encoding imaging sequence JEPHI turns out to be optimal for multi-spin systems. Image-guided localized wide-line spectroscopy is possible by the aid of the LOSY procedure. The spatial resolution depends on the achievable field gradients and the sensitivity. Resolutions much less than one millimeter are expected to be possible with gradients much greater than 0.15 T/m.

REFERENCES 1) E. Rommel, S. Hafner, R. Kimmich, J. Magn. Reson. 86,264 (1990). 2) J. Jeener and P. Broekaert, Phys. Rev. 157,232 (1967). 3) L. E. Kay, R. E. D. McClung, J. Magn. Reson. 77, 258 (1988). 4) S. Hafner, E. Rommel, R. Kimmich, J. Magn. Reson., in press 5) E. Rommel and R. Kimmich, J. Magn. Reson. 83, 299 (1989).

107

RESPONSE TO TIP-ANGLE AND SPIN-LOCK RF PULSE SEQUENCES IN THE PRESENCE OF MAGNETIC FIELD GRADIENTS: SLICE-SELECTIVE EXCITATION IN NMR IMAGING EXPERIMENTS. D. E. Demco·, F. Balibanu·., R. Kimmich"· ·Polytechnic Institute, 3400 Cluj, Romania •• Institute for Isotope and Molecular Technology, 3400 Cluj, P.O.B. Box 700, Romania ••• Sektion Kernresonanzspektroskopie, Universitat Ulm, 7900 Ulm, Fed. Rep. of Germany

PURPOSE We describe the theoretical response of spin systems to radio frequency pulses in the presence of magnetic field gradients. The conditions under which slice-selective excitations occur are derived. The relevance of the results for NMR imaging experiments is outlined.

INTRODUCTION One of the most crucial principles of NMR imaging experiments is the application of RF pulses in the presence of magnetic field gradients (1). Usually one crudely distinguishes "hard" and "soft" pulses, where the latter often have shapes defined by Gauss or sinc functions. Another pulse sequence of interest in this context is the combination with spin-lock pulses as it can be used in localized spectroscopy (LOSY) experiments (2). In this paper we report on a general treatment of two-pulse sequences in the presence of magnetic field gradients. In the first step the pulse shape is assumed to be rectangular. The analysis implies Hahn echo sequences and slice-selective LOSY spin-lock pulses as special cases as well. The investigation is based on the general density matrix formalism. The slice profiles are obtained as Fourier transforms of the signals in presence of constant field gradients.

RESULTS The analysis leads to amplitude and phase correction factors for Hahn echoes and LOSY signals. The dependence on the applied field gradients and on the flip angles, phases, amplitude, and off-resonance conditions of the pulses will be shown. In the absence of relaxation effects, oscillatory profile patterns appear. The dependence on transverse and longitudinal relaxation in the laboratory or rotating frame will be presented. The latter is particularly important for the efficiency of slice-selective excitations. The optimum of the length of the LOSY spin-lock pulse will be related to the parameters mentioned above.

108

Besides the response arising from uncoupled spins to two-pulse and spin lock sequences in the presence of field gradients, the influence of weak or strong J coupling of two-spin (1/2) systems has been considered. It will also be shown, that dipolar or quadrupolar coupling in solids leads to a particularly efficient spoil effect of the magnetization outside of the slice to be selected by spin-locking in the LOSY procedure. The profile of the slices excited by the LOSY sequence is comparable to that obtained with Gaussian or sinc shaped pulses. The slice width, however, can most easily adjusted by taking advantage of the proportionality to the amplitude of the spin-lock pulse or of the inverse proportionality to the magnetic field gradient.

REFERENCES 1) P. G. Morris, Nuclear Magnetic Resonance Imaging in Medicine and Biology, Clarendon Press, Oxford, 1986.

2) E. Rommel and R. Kimmich, J. Magn. Ruon. 83, 299 (1989).

109

ON THE PROTON T2 EFFEcrs OF OXYGEN-17 AS AN NMR AND MRI LABEL FOR WATER IN LIVING SYSTEMS A.L. Hopkins(l), E.M. Haacke(2), W.D. LustO), P.A. Wielopolski(2), R.G. Barr(4), and C.B. Bratton(S). (1) Depts. of Anatomy and Radiology, (2) DepL of Radiology, (3) Division of Neurosurgery, (4) DepL of Biochemistry, Case Western Reserve University and University Hospitals, Cleveland, OH 44106. (5) DepL of Physics, Cleveland State University, Cleveland, OH 44115, U.S.A. ABSTRACT: The water proton T2 in living organism can be greatly reduced by the administration of oxygen-17 enriched water. This effect can be used to follow diffusion in model systems and is used here to monitor the altered circulation in the brain resulting from the ligation of one of the carotid arteries in living gerbils. INTRODUCTION: Luz and Meiboom between 1960 and 1964 (1) demonstrated that naturally abundant H2170 was responsible for lowering the T2 of water protons at pHs near neutrality and that enrichment with H2170 caused further fall in T2. We have extended these observations to protein solutions, living tissues and intact animals (2). Through the use of T2 sensitive pulse sequences (spin-echo or SE) it is possible to image the distribution of the enriched water with Magnetic Resonance Imaging (MRI) methods. We have been unable to locate any prior literature on the application of this water proton T2 effect of 170 in biological systems. Here we demonstrate its utility in defining areas of ischemic or "stroked" brain tissue and examine the results for evidence of the macroscopic diffusion which can be seen in model systems (3). METHODS:

The oxygen-17 enriched water used was 45 atoms % (4) and was injected i.p. (intraperitoneally) without the addition of salts. Even though higher enrichments are available (5) this concentration was used as a compromise between cost and osmotic stress to the animals. Unilateral common carotid artery ligation was carried out on anesthetized Mongolian gerbils and those animals showing marked neurological symptoms on recovery from surgical anesthesia were reanesthetized for imaging. Half-Fourier imaging was done with the orbital coil of a Siemens 1.5T Magnetom using a TR of 4.0 s and a TE of 90 ms and a slice thickness of 2 mm. After the control images were obtained the oxygen-17 water was given over a period of one minute via an indwelling i.p. catheter. Imaging was continued for up to 70 minutes post injection. Image intensity was read from the same predetemrlned areas of each section with an ROI (Region Of Interest) of a fixed diameter of 2.7 mm. With the exception of section 4, intensity measurements were from one ROI location on each side. In the case of section 4 two ROI placements were used on each side, in the cortex and in the basal ganglions. RESULTS. The inserted diagram to the left in figure 1 is of the gerbil brain showing the approximate locations of the sections imaged and measured. Only the olfactory bulb of section 1 failed to show an asymmetric response on injection of H2170 but the vitreous of the eyes showed a marked difference with the eye contralateral to the ligation rapidly losing intensity as the circulating oxygen-17 lowered the T2 . In all other sections the i.p. injection of about 1.5 % of the body weight ofH2170 leads to as much as a 45 % fall in intensity in the normally perfused areas. Due in part to residual collateral circulation there is also approximately a 10% decrease

110

in intensity in the ischemic tissues which have little circulation. Representative changes from section 4 are plotted in figure 1. These intensity differences between the ischemic and normal sides of the brain are observed both in the presence and absence of edema or other prior evidence of ischemia before the injection of H2170.

~

.~~ _

Ipsiloterul ....."'-.....:.:::..:::::..::::;;:.:::.::1;.:.,;,::::.:::.&...... - .

60 50 40 300

D"\v 2

O~ Il:

4

10 20 30 40 50 60 MINUTES AFTER INJECTION

70

FIGURE 1. The effect of ~170 injection on the relative image intensity of section 2 and the cortex and basal ganglions of gerbil brain at section 4. The ischemic side is represented by the closed symbols and the normal by open symbols. In each case the reading of the same section and same location before H 2170 is taken as 100 %. Location of the ROIs on one side are shown in the inserted diagram at the right. Section 2 =0 . Cortex = 0 and basal ganglions = II of section 4.

The relative stability of the differences is notable in light of the scale on which these measurements were made. At its widest point the gerbil brain is ca. 14 mm across, this is at section 4 which is diagrammed in the right insert in figure 1. The difference in intensity between the ganglions is maintained even though the distance between the centers is only 3 mm. In addition the visual inspection of the images reveals no evidence of the migration of the boundary between high intensity ischemic tissue and the low intensity normal tissue as might be expected if the intensity differences were dominated by diffusion of H 2170. There is a loss of contrast between the two sides but this loss does not appear to be due to the migration of H 2170 into the ischemic tissue. Instead there is a loss of the oxygen-17 effect in the normally perfused tissue leading its intensity to rise towards the the ischemic intensity. CONCLUSIONS. The differences in intensity between ischemic and normal tissue produced by the injection of H2 170 are very marked and remain for at least 70 minutes after its administration. The stability of these differences between closely adjacent areas of the same tissue indicates that macroscopic diffusion or transport mechanisms other than vascular circulation do not playa dominant role in the macroscopic distribution of the T2 effects of H2170, even on a millimeter scale.

... Supported by grant number 4650 from the American Heart Association, Northeast Ohio Affiliate. REFERENCES: 1. Z. Luz and S. Meiboom, J. Amer. Chem. Soc. 86, 4768 (1964). 2. A. L.Hopkins, E. M. Haacke, J. Tkach, et al. Magn. Reson. Med., 7, 222,1988. 3. C. B. Bratton, R G. Barr, A. L. Hopkins and C. T. Burt. Proc. Eighth SMRM, p 143, August (1989). 4. Icon Services, Summit NJ. or Isotec Inc., Miamisburg OH, U.S.A.. 5. Cambridge Isotope Laboratories. Woburn MA, U.S.A..

111

DOUBLE RESONANCE RARE NUCLEI IMAGING F. De Luca, R. Campanella, ~ Bifone, B. Maraviglia Universita "La Sapienza" di Roma, Dipartimento di Fisica 00185 - Roma, Italy

The "free" water protons are the obvious selected nuclei to perform MRI because are the more abundant nuclei in biological tissues and because they posses the highest NMR sensitivity. For these reasons the images obtained from the protons offer the best morphological representation of the human body. It

is

fluorine,

to

be

pointed

phosphorus,

out

however,

potassium

and

that

nuclei

nitrogen

are

like more

sensitive than hydrogen to different physiological state due to the role they play in energy transformation or transport phenomena and in functional processes. So, despite their low sensitivity

and

concentration,

the

"rare"

nuclei

have

received considerable attention in biochemical MR spectroscopy and MRI. In the present work we propose a novel rare nuclei which imaging method, is based on the heteronuclear J-coupl1ng between the rare nuclei and lH. Actually the J-modulation produced on the lH spin-echoes envelope by a double resonance spin-echo sequence can be utilized to make imaging of the rare nuclei as a difference between the lH usual image and the lH-rare nuclei J-modulated images.

112

PERSPECTIVES OF THE USE OF MAGNETICALLY LABELED ANTIBODIES IN NMR IMAGING M.A. Macri*, F. De Luca, G. Garreffa and B. Maraviglia Universita di Roma "La Sapienza", Dipartimento di Fisica 00185 ROMA, Italy * Universita di Chieti, Istituto Fisica Medica 66100 CHIETI, Italy

Monoclonal

antibodies

tagged with

radioactive

isotopes

have been used for several years for specific tissue recognition by y camera scanning. Tentatives of appling monoclonal antibodies to NMR imaging as specific contrast agents were recently made 1,2). Generally the objective of the research consisted in binding polimeric or other ion chelate molecules, capable of binding paramagnetic ions like Gd+3, to the antibody or to a monoclonal antibody fragment. Up to now anyway our results and the results of other laboratories showed a serious limitation in the effects that these paramagnetic impurities induce both "in vitro" and "in vivo". The importance of having specific contrast agents is however so relevant that it is worth considering other possible means by which this objective could be reached. Therefore, besides considering the existing limitations of this research we will report and analysis of some recent new possibilities which arised in this field.

References 1) 2)

P.

Shreve and A.M.

Alsen,

Magn.

Res.

In Med.

3,

336

(1986) M.A. Macri, F. De Luca, B. Maraviglia, F. Polizlo, G. Garreffa, S. Cavallo and P.G. Natali, Magn. Res. in Med. 11, 283 (1989)

113

IMAGING OF 7L1 IN A POLYMER ELECTROLYTE FILM P E08(LiClO 4 ): A PRELIMINARY INVESTIGATION. M. Sonderegger, J.Roos, M.Mali and D.Brinkmann Physik Institut, Universitat ZUrich, 8001 Zurich, Switzerland ABSTRACT We investigated the possibility of imaging mobile Li ions in a P E0 8(LiClO 4 ) polymer electrolyte film. We have tentatively distinguished regions with different degrees of ion mobility. PACS Numbers: 76.60 j 87.71.K j 66.30.D INTRODUCTION The field of ion conducting polymers has become an important part of solid state electrochemistry. Polymer electrolytes like Poly(ethylene ozide)8(LiClO4 ) are inhomogeneous with three coexisting phases at room temperature: pure crystalline PEO and a crystalline stoichiometric complex, both embedded in an amorphous phase which is the only conducting part. The mobility of Li ions is very different in these phases. In order to obtain some information about the distribution of phases across a polymer electrolyte film we investigated the possibility of making mobility weighted NMR images of Li ions. EXPERIMENTAL A film of 0.1 mm thickness was prepared from a solution of PEO (molecular weight 4 X 106 ) and Li salt in acetonitrile and a piece of approximately rectangular shape (7 mm x 3 mm) was used as a sample. In PEOs(LiCI04 ) there is only one formula unit of (LiCI0 4 ) per eight units of ethylene oxide corresponding to a very low Li content of 1.6 mole%. Therefore rather poor Li NMR signals are to be expected. The experiment was performed in a 10 cm-bore kryomagnet at a field of 4.7 Tesla using an imaging probe head and a double-conversion type spectrometer developed in our laboratory. Gradient pulses are generated by a Bruker power supply (B-MN 3x+/-40/60) controlled by wave form generators (KROHN-HITE 5920). Puls timing is performed through a timing simulator (Interface Technology RS-670) and data are acquired with a digital scope (LeCroy 9400). Control of the experiment and complete data analysis is obtained by software developed and running on an Apollo Workstation (DN 3010). RESULTS The multi-exponential decay of the 7 Li spin echos is governed by 3 time constants (Fig.l): one in the J.LS range (not shown) to be attributed to the crystalline phase with immobile Li, and two in the ms range which stem from amorphous phases with two distinct Li mobilities. Using the 1r/2 - 'T - 1r spin echo pulse sequence with 'T values of 2 ms and 5 ms images of Li in the film (Fig.2) were obtained by Fourier transform imaging technique applying phase coding and readout gradients in the plane of the film.

114

No attempt was made to correctly weight images with respect to the corresponding time constants (no T2 weighting). In picture (B) of Fig.2 only the amorphous material with the high Li mobility should appear. Picture (C) should represent only the amorphous phase oflower mobility. It has a poor S IN ratio because of the subtraction procedure and the rather low abundance of this phase. Intensity from crystalline material is lacking from any picture because of the very short time constant. DISCUSSION Pictures (B) and (C) of Fig.2 show that a coarse discrimination between different "mobility regions" of the film is feasible, at least on a mm scale. In (A) the rectangular shape is not well represented. This is possibly due to crystalline phases preferentially situated near the circumference of the sample. Fig.I: Amplitude of 7 Li echo sig~ nal as function of delay time T in a 11"/2 - T - 11" spin echo experiment. Decay curve is double exponential with two time constants attributed to two different amorphous phases.

'"7

" ~

.,

~Q. E

X-t-(1tI'2»'".'t-acq., the main difference for 1>1 is due to the coupling-modulated nature of the echo decay (2). Consequently, no "true" powder spectrum from echo signal can be obtained since refocusing of contributions from domains with different splittings will also be unequally refocused. When measuring satellite linewidths, the results are represented in 2D format; the satellite homogeneous linewidths are then measured on the central lines in Fl spectra generated from satellite amplitudes in F2. For systems with large quadrupole coupling, where (1t(2) pulses cannot be approximated as nonselective, QE studies with short pulses can be performed. For spin I> 1 case, the main consequence will be the decrease of the intensity of the central line in the Fl spectra. For spin 1=1 case, the echo decay becomes coupling-modulated, making the 2D format preferable also here. In the traditional QE experiment, all the various P±l k single-quantum coherences, produced during the evolution period, participate in the refocusing process. In a modification of the QE method, the initial (1tI'2h preparation pulse is replaced by a (2I-I)-quantum filter. This pulse sequence has two important applications: (i) modifying intensity ratios in the Fl spectra, particularly useful in spin 1=3(2 and 7(2 cases, and (ii) selectively suppressing signals with zero quadrupole splitting. When, instead of the (1tI'2h pulse, a two-pulse sequence is applied, which generates multiple-quantum (MQ) coherences, a quadrupole echo on the MQ coherences can be generated. Thus one can accurately determine the homogeneous linewidths of various MQ transitions. Applying two different phase cycles for the second pulse in the traditional QE sequence, coherence transfer filtered echoes can be produced. Refocusing of dephasing due to terms linear (e.g. magnetic field inhomogeneity) and bilinear (e.g. quadrupole coupling) in the spin operator is achieved in a single experiment if the q=±1 ~q=+1 coherence transfers are selected by the appropriate phase cycle (3). On the other hand, when the q=±1 ~=±1 transfer path is retained, the frequency shift of the central line in the Fl spectra from various satellite positions in F2 accurately yields the relative dynamic shift of the corresponding satellites. REFERENCES 1. K. Blum, "Density Matrix Theory and Applications", (Plenum, N. Y., 1981); B. C. Sanctuary, J. Magn. Reson. 61, 116 (1985). 2. I. Fur6, B. Halle, and T. C. Wong, J. Chern. Phys. 89, 5382 (1988); I. Fur6, B. Halle, P.-D. Quist, and T. C. Wong, J. Phys. Chern. 94, 2600 (1990). 3. R. L. VoId and R. R. VoId, J. Magn. Reson. 42, 173 (1981).

121

NMR STUDIES OF DOUBLE PROTON AND DEUTERON TRANSFERS IN LIQUIDS AND SOLIDS H.H.Limbach, H.Rumpel, B.Wehrle, L.Meschede, M.Schlabach, G.Scherer, J.Braun, F.Aguilar-Parilla, C.Hoelger Universitat Freiburg, Institut fiir Physikalische Chemie, Albertstr. 21, D-7000 Freiburg i.Br., FRO ABSTRACT Kinetic HH/HD/DD isotope and liquid/solid state effects on intra- and intermolecular double proton transfer reactions of organic compounds have been studied using high resolution liquid and solid state NMR techniques. From these studies information on the reaction pathways are obtained. It is shown that incoherent thermally activated proton tunneling plays a major role in these reactions. INTRODUCTION Many organic compounds are subject to proton tautomerism in the liquid and the solid state. During these processes, generally, two or more protons are transferred between the reactants either along intramolecular pathways or along intermolecular pathways according to the equation

*

A

*

/H... . .H, /B ~ A' B ···H 'H·"

In recent years efforts have been made to study the kinetic HH/HD /DD isotope and solid state effects on such reactions using improved methods of high resolution liquid and solid state NMR spectroscopy (1) - (6). From these studies detailed information on the reaction mechanism can be obtained as shown in the following. METHODS In order to obtain kinetic information the methods of lineshape analysis, magnetization transfer in the rotating and the laboratory frame, as well as longitudinal relaxation time measurements were employed. For the reactions in amorphous solids a theory of NMR lineshapes in the presence of inhomogeneous and homogeneous line broadening was developed (5,6). High resolution solid state studies were carried out using the techniques of cross polarization (CP), magic angle spinning (MAS) and proton decoupling at magnetic fields of 2.1 and 7.1 Tesla. In the latter field variable temperature high speed spinning methods were employed in order to obtain rotational side band free spectra. In these experiments it was found that high speed spinning leads to a substantial sample temperature increase (7). Temperature measurements were, therefore, performed using a novel chemical shift thermometer (8). In addition, stratagems are proposed in order to distinguish between spin diffusion and chemical exchange processes in solids (9).

122

RESULTS AND DISCUSSION Stratagems are presented how to count the number of protons in flight in the rate limiting step of the reaction as well as the associated kinetic HH/HD/DD isotope effects. The latter show that in the intramolecular double proton transfer reactions the protons move stepwise (3,4). By contrast, in the intermolecular cases both protons contribute kinetic isotope effects (2). This results is interpreted with a substantial heavy atom motion during the reaction which modulates the reaction energy surface. From the temperature dependence of the rate constants evidence for incoherent thermally activated proton tunneling is obtained in some cases. The solid state NMR studies show that the degeneracy of symmetric proton transfer systems is, generally, lost in the solid state. Whereas the reaction energy surfaces of reacting molecules embedded in the ordered crystalline state are all perturbed in the same way broad distributions of reaction energy surfaces are found for molecules in amorphous states, e.g. if they are dissolved in organic glasses. The proton transfers do not only take place in environments characterized by a high symmetry of the surface but also in strongly asymmetric environments. CONCLUSIONS Dynamic NMR techniques allow the elucidation of kinetic HH/HD/DD isotope and liquidl solid state effects on double proton and deuteron transfer reactions in liquids and solids. Such information is valuable to understand the mechanisms of chemical reactions in condensed matter in a timescale of slow molecular motions. ACKNOWLEDGEMENTS This work has been supported by the Deutsche Forschungsgemeinschaft, Bad Godesberg, the Stiftung Volkswagenwerk, Hannover, the Bundesministerium fiir Forschung und Technologie, Bonn, the European Commission, Brussels, and the Fonds der Chemischen Industrie, Frankfurt. REFERENCES 1.

2. 3. 4. 5. 6. 7. 8. 9.

H.H.Limbach: Dynamic NMR spectroscopy in the presence of kinetic isotope effects, in NMR Basic Principles and Progress, Heidelberg 1990 and references cited therein. H.H.Limbach, L.Meschede, G.Scherer, Z.Naturforsch. 44a (1989) 459. H.Rumpel, H.H.Limbach, J.Am.Chem.Soc., 111 (1989) 5429. G.Scherer, H.H.Limbach, J.Am.Chem.Soc., 111 (1989) 5946. B.Wehrle, H.Zimmermann, H.H.Limbach, J.Am.Chem.Soc. 110 (1988) 7014. B.Wehrle, H.H.Limbach, Chem.Phys., 136 (1989) 223. F.Aguilar-Parrilla, B.Wehrle, H.H.Limbach, H.Braunling, J.Magn.Reson, in press. B.Wehrle, F.Aguilar-Parrilla, H.H.Limbach, J.Magn.Reson, in press. H.H.Limbach, B.Wehrle, M.Schlabach, R.Kendrick, C.S.Yannoni, J.Magn. Reson., 77 (1988) 84.

123

TRANSFER OF SPIN ORDER IN SOLIDS. DETERMINISTIC AND DIFFUSIVE BEHAVIOR.

G. Aebli, B.H. Meier, and R.R. Ernst Laboratorium fUr Physikalische Chemie Eidgenossische Technische Hochschule 8092 Zurich, Switzerland

It is wellknown that the transfer of spin order in solids, normally called "spin diffusion II , is a fully deterministic quantum mechanical process. It can be described as the evolution of a nonequilibrium state under the dipolar interaction. feasible,

In

consequence, time-reversal and spin-echo experiments are

and entropy should remain constant.

Nevertheless, due to the

complexity of the network of dipolar interactions, an irreversible behavior results in practical situations. This suggests the description by diffusion equations.

In this contribution, we provide further evidence that the deterministic or diffusive character of the behavior depends both on the type of the e..'..,x,y) as defined in ref.[3]. The long wavelength limit of this expression enables the phonon contribution to the AFMR linewidth to be determined as a function of the temperature and anisotropy. We stress that the above result holds for general spin values. In the case of a simple antiferromagnet having no intra-exchange interactions contact with the work of Cottam [2] may be made. For a spin-1 antiferromagnet eq.(l) is quadratic in (t>..)2 and thus the non-interacting excitation spectrum can readily be found. In this case, when D/bJ+(O) o' This expression provides the correct temperature dependance of as opposed to the result

Eo

(6)

based on the result of an effective anis~tropy field [2]. (Note, this theory completely neglects the presence of the optical branches.) However, if the anisotropy field is replaced by -DPs/b, that theory is correct to first order in D/bJ+(O). For higher values of spin the dispersion relation of eq.(l) is more difficult to analyse as there are in general4S branches to the spectrum. Even to order D2/(bJ+(0))2 there is an additional temperature dependant term in the dispersion relation when S > 1 that necessitates the solution of a cubic equation. The result of eq.(4) is then best studied by numerical methods. At present we are extending the theory to account for longitudinal spin fluctuations that become important near the ordering temperature. This involves the consideration of diagrams in the polarization matrix containing two internal momentum summations, as has already been discussed in the case of a ferromagnet [3]. Referances 1) T.J. Drye and J.W. Tucker, in Phonons '89, eds. S. Hunklinger et al. (World Scientific) (1990) 169. 2) M.G. Cottam, J. Phys. C:Solid State Phys., 7, (1974) 290l. 3) KG. Chakraborty and J.W. Tucker, Physica 146A (1987) 582. Acknowledgement One of us (T JD) is grateful to the Science and Engineering Research Council for financial support.

133

EPR OF SOLITONS IN ONE-DIMENSIONAL ANTIFERROMAGNETS ? J.Kuriata, L.Sadlowski, B.Bojanowski, M.Wabia Institute of Physics, Technical University of Szczecin, AI. Piast6w 17, Szczecin, PL 70-310, Poland M.L.Falin and V.V.Izotov Physics Technical Institute, Soviet Academy of Sciences, 420029, Kazan, USSR ABSTRACT Temperature dependence of the EPR linewidth for Cr2v4_xMox013+x/2 is presented. It is shown that the substance belongs to a class of one-dimensional antiferromagnets. The antiferromagnetic phase transition is characterized. It is suggested that near Tc one detects a new EPR signal the behaviour of which resembles the behaviour of signals arising from moving solitons in linear antiferromagnets. PACS numbers: 76.30 and 75.50 INTRODUCTION Cr2V4_xMoxOI3+x/2 is a new substance which can appear in the three component system of transition metal oxides Cr20x-V205-Mo03[1,2]. It is believed that the compounds appearing in such a system possess unusual catha lytic properties and thus are intensively studied using many different methods. This communication presents our recent EPR studies of a magnetic phase transition taking place at low temperatures (T c = 3.6K). RESULTS AND DISCUSSION Three different EPR lines are detected over the temperature range 300 to 3K. Firstly, down to 5.7 one detects a line resulting from Cr 3 + ions which broadens critically according to the law [3J: i B(T) =LlB.,o+A[CT/Tc)-l] -KCT-Tc ) (I) The line broadening is shown in Fig.1 and 2 The best fit procedure gave us the following parameters appearing in (1): B = 17.6 mT, A = 54.7 mT, Tc = 3.6K and '6 = -0.633. Secondly, at 10K one detects a trace of a sharp line which becomes more and more intense with the temperature decrease (see Fig. I) . And finally, this sharp line is superimposed on a broader one which appears at 5.9K and this line narrows down to 5.2K and then remains unchanged (see Fig.3).

250

330

410 B(mT}-

134

The behaviour of this line resembles strikingly the behaviour of the soliton line described in [4]. The linewidth of this line could be described by the function [4]:

~8p_p(T)

=

~ 80

Cexp(-IIl/k 8 T)

+

(2)

theoretially predicted for the case of moving domain - wall solitons. The'following parameters of (2) descibe our data: ~80 = 21.2 mT,

t 120

I

=

-46K and C

t

Fig.2

~

E

~ 80

- c..c.. CO

28

T.

Fig. 3

2

~ 24

al

I

If}. (5-11) nuclei. The reasons are numerous and include (i) spectral simplifications, (ii) investigations of coupling features, and (iii) elimination of large first-order quadrupolar interactions for I > If}. nuclei. For quadrupolar nuclei anention has especially been devoted 10 the double-quanblm (2Q) transition of spin 1 = I systems (5-8) although also a few 2Q and 3Q Sbldies have appeared for I > I nuclei (9-11). With a few exceptions these studies deal with single crystals or molecules oriented in a liquid-crystal phase and mainly apply selective pulse procedures. In this paper we present preliminar resulls of the first solid-state NMR study of MQ-coherences for I = 3f}. and 5f}. nuclei in powders rotating at the magic angle (MAS). The non-selective lDf}.D experiments, which allow accurate measurements of the quadrupolar interaction parameters (CQ and 11) from simulations of the first-order quadrupolar-induced spiooing sideband (ssb) manifolds observed for the MQ-filtered/MQ satellite transitions, are intimately related 10 our recent one-pulse MAS method relying on ssb's from the IQ satellite transitions (12). Various three-pulse sequences (Fig.t) are analyzed for efficient excitation and detection of MQ-coherences in multilevel systems using flJ'St-order density matrix calculations with the assumptions of ideal as well as non-ideal pulse conditions. THEORY: In the usual Zeeman interaction representation (assuming IHZI » IRQI » IRa') the Hamillooian of an isolated quaclrupolar nucleus can be descn'bed 10 first order by 2 HVl(t) = I co exp(im'¥) [3~ - 1(1+1)] [1] 111=-2 where co denoting Euler angles relating the rotor fixed frame (R) to the princip8J axis frame (p), whereas is a reduced matrix element with PRL 54.7' relating R 10 the 1aboratory frame (I.).

it

=

Preparation

e,

Evolution

e2

Jl

1:

R

, e

Detection

0------0

RV3

t,

Fig.I General non-selective pulse sequence for lDflD MQ-experiments of quadrupolar nuclei in rotating solids. The presented experiments and simulations used 'YI H lf}.2t - 40 kHz, 'I ="2 = x, and MQ-Phasecycles on ~.

The general (8 t )'1 - t - (82)92 excitation sequence (Fig.l) may be described by the propagator

Ue

= V'2(82;t) W(O,t) V'I(8 1;O)

[3]

whese V,.(8P) and W('a,t~ denote propagators for the j'th rf pulse placed at time t and free precession in the fa 10 'b. respectively. I.e., tb

period win

V,,(9P) = )

exp{-i[H . . . 10-· P700Ao~ FeS

- 1(FeS) ~> "00-· . P+7oo AQA

where P700 is the primary donor and Ao ' A1 and (FeS) are the first three acceptors. The first radical pair which may be detected by transient EPR is P 700At. It is important to point out that in solution under physiological conditions the molecular motions in this system are sufficiently slow that the anisotropy in the magnetic interactions is reflected in the spectrum. Because of this, important structural information for the charge seperated states can be obtained from an analysis of their spectra. The analysis of the time development of the spin polarization in sequential spin pairs has been recently discussed [2,6]. Here, we will treat this problem in connection with an experimental example. Results: Figure 1a shows two spectra obtained for fully deuterated algae Synechococcus }ividus measured at 9.5 GHz (X-band). The solid line spectrum observed at early times arises from the spin pair P+ Ai. The dashed line spectrum is observed at later times and is assigned to the pair P+(FeS)- [3]. Figure 1b shows corresponding simulations of the experimental spectra. The two simulations of the spectrum at late times correspond to differing values of the dipolar coupling between the two spins. The dashed curve is obtained for D=O.OG and the dotted curve for D=-1.0G Note that only net emmissive polarization is obtained when the spins are uncoupled.

165

Figure

1:. b) Simulation

a) Experiment

331. 0

332.0

333.0

334.0

BO/mT

~31.0

332.0

333.0

334.0

BO/mT

Experiment.al and simulated EPR spectra for fully deu tera ted algae Synechococcus at X band (9.SGHz) a)Solid line: 0-200ns. dashed line: 2-3tJ.s. aFter light excitation. b) Solid line: simulation of early spectrum; dashed line: sImulation of late spectrum w-ith D=O.O; dotted line: simulation of late spectrum w-it.h D=-1.0G.

Discussion: For the simulations shown in figure 1 it is assumed that the I electron transfer to A1 is too fast to permit any significant STo mixing in the P+ Ai) pair. The early spectrum then arises from the transitions in the four level system for the P+A1 pair in which mixing between the S and To states occurs. The polarization results from a selective population of the mixed states according to their singlet character. The polarization from this pair is then transfered to the second pair according to the transition probabilities between the eigenstates in the two differently coupled radical pairs. Conclusions: The transfer of spin polarization between successive radical pairs can be described in terms of the transition probabilities between the states in the two pairs. This approach yields results in good agreement with the experimental EPR spectra obtained for deuterated PS I at X-band frequencies. References:

1.

2. 3. 4. S. 6.

Stehlik, D. Bock, C.H. and Peterson, J. (1989) J. Phys. Chern. 93, 1612-1619 Feezel, L.L., Gast, P., Smith, U. and Thurnauer, M.C .• (1989) Biochim. Biophys. Acta 974, 149-1SS. Bock, C.H., van der Est, A.J., Brettel, K. and Stehlik, D. (1989) FEBS Lett. 247, 91-96. Rutherford, A.W. and Heathcote, P. (198S) Photosynth. Res. 6, 29S-316. Golbeck, J.H. (1987) Blochirn. Biophys. Acta 89S, 167. Norris, J.R., Morris, A.L., Thurnauer, M.C. and Tang, J. (1990) J. Chern. Phys. (in press).

166

Dipolar relaxation enhancement in inhomogeneous systems. Application to the oxygen evolving complex of plant photosynthesis. R.G. Evelo and AJ. Hoff Department of Biophysics, Huygens Laboratoroy of the State University, P.O. Box 9504, 2300 RA Leiden, The Netherlands. In two recent papers [1,2] we have demonstrated that information can be gleaned on the oxidation states of the Mn cluster of the oxygen evolving complex (OEC) of plants by carefully measuring the spin-lattice relaxation curves of a stable, tyrosyl radical, D , which is normally present in reaction centers of photosystem IT in photosynthetically active preparations. Significance differences were found in the average relaxation time of D when the OEC had successively accumulated one to three positive changes, and a model was developed explaining the results in terms of two Mn oxidations (Mn IT to Mn ill and Mn ill to Mn IV) and one non-Mn oxidation step. A peculiar finding was that in contrast to the tyrosyl radical in vitro, the relaxation curves of D all showed a pronounced non-exponentiality. This was tentatively attributed to a charge-resonance phenomenon in two of the four Mn present in the OEC. We here propose an alternative expanation, namely that it is a consequence of the orientation dependence of the dipolar relaxation enhancement. The theory of dipolar relaxation enhancement in the solid state is due to Solomon [3], who calculated the enhancement of the relaxation rates T 1-1 and Til of a nuclear spin I magnetically coupled to a neighbouring electron spin S in a randomly oriented, homogeneously broadened system with I S 1/2. We have extended his treatment to randomly oriented, inhomogeneously broadened systems with arbitrary quantum numbers of the two coupled spins. The enhancement of the spin-lattice relaxation of a paramagnetic species due to dipolar interaction with another paramagnetic species is calculated for an experiment where the microwave field intensity is much less than the inhomogeneous linewidth of the EPR line under consideration. We show that also in the absence of spin diffusion under these condition a pronounced nonexponential saturation-recovery trace results. Using the theory outlined above we have been able to satisfactorily simulate the various relaxation curves obtained in Ref. 1 and 2. It is anticipated that the pronounced orientational effect on the relaxation enhancement will make it possible to derive from relaxation experiments on oriented membranes accurate information on the position of the Mn cluster with respect to the tyrosyl radical in reaction centers of photosystem IT.

= =

[1]

[2] [3]

De Groot, A., Plijter, IJ., Evelo, R. Babcock, G.T. and Hoff, A.I. (1986) Biochim. Biophys. Acta 848, 8-15. Evelo, R.G., Styring, S., Rutherford, A.W. and Hoff, AJ. (1989) Biochim. Biophys. Acta 973, 428-442. Solomon, I. (1955) Phys. Rev. 99, 559-565.

167

TRANSIENT EPR OF SPIN POLARIZED TRIPLET STATES AND CORRELATED RADICAL PAIRS IN VISCOUS LIQUID CRYSTALS R. Bittl, N. Rosch, S. Weber, A. Munzenmaier and G. Kothe Universitat stuttgart, Institut fur Physikalische Chemie, Pfaffenwaldring 55, 7000 stuttgart 80, Fed. Rep. of Germany ABSTRACT Coherent and incoherent spin dynamics of photoinduced triplet states and correlated radical pairs are studied by transient EPR following pulsed laser excitation.

INTRODUCTION Transient EPR spectroscopy in combination with pulsed laser excitation represents a powerful method for the study of photoinduced electronic spin states under solid state conditions [1]. An inhomogeneous linewidth larger than 0.5 mT guarantees the potential of a 10 ns time resolution [2]. No restriction exists with respect to excitation band width. Thus, transient EPR can yield useful information about short lived triplet states [3] and photoinduced spin pairs [2] in "rigid" environments. RESULTS AND DISCUSSION In this contribution we first present transient EPR studies of retinal triplets in a viscous liquid crystal. The time evolution of the transverse magnetization is monitored at various static and microwave magnetic fields. Analysis of the angular dependent experiments is achieved by employing a relaxation model based on the stochastic Liouville equation [4]. From the transient EPR spectra the spin polarization and orientational distribution of the triplet molecules are obtained. Simulation of the time evolution of the transverse magnetization provides the motional correlation times of the spin systems over an extremely broad dynamic range [4,5]. At slow motions the method is limited by the occurrence of dominant T2 processes other than molecular reorientation. A fast motion limit is reached when T1 becomes comparable to the time resolution of the detection system, which is of the order of 10 ns. The liquid crystal is then employed as an anisotropic viscous matrix for photoinduced, weakly coupled radical pairs. Under these conditions transient EPR is able to reveal the geometry of the radical pair via the magnetic interactions as well as detailed information on the spin polarization mechanism and the restricted molecular dynamics. The charge separated states states along the electron transfer chain in photosynthetic centers represent such a "solid like" case [2]. Analysis of the. transient EPR data at high and low microwave power establishes the anisotropic nature of the magnetic interactions in these systems.

168

\ [luI

o

2 . / 042

8 0 [TI

Fig. 1. Transient EPR of triplet retinal in a liquid crystalline matrix at different orientational distributions with respect to the laboratory frame. T = 220 K. REFERENCES

[1] S. S • Kim and S. I. weissman, Rev. Chem. Intermediates 1., 107 (1979). [2] D. Stehlik, C.H. Bock and M.C. Thurnauer in "Advanced EPR in Biology and Biochemistry" (ed. A.J. Hoff), Elsevier, Amsterdam 1989. [3] J. Frick, J.U. von Schutz, H.C. Wolf and G. Kothe, Mol. Cryst. Liq. Cryst. 1990, in ·press. [4] J. Fessmann, N. Rosch, E. Ohmes and G. Kothe, Chem. Phys. Letters 152, 491 (1988). (5] N. Rosch, R. Bittl, A. Munzenmaier, E. Ohmes and G. Kothe, J. Chem. Phys. 1990, submitted.

169

MAGNETIC RESONANCE AND PHOTOCHEMISTRY: OF SOLID HUMULENE NITRO SITE

THE RED-PHOTOLYSIS

Z.F. Khan, D.K. MacAlpine, A.L. Porte, J.E. Schubert and G.A. Sim, Department of Chemistry, The University of Glasgow, Glasgow G 12 8QQ, Scotland. ABSTRACT: Combining single-crystal and polycrystalline e.p.r. spectroscopy with high-resolution n.m.r. spectroscopy, X-ray crystallography and classical chemistry, has enabled the steps in the red-photolysis reactions of the two forms of solid humulene nitro site to be unravelled. Humulene nitrosite, (1), is a deep-blue solid. It exists in two crystalline forms, needles and platelets respectively, that have almost identical spectroscopic properties. X-ray analyses, [1], [2], show that they are the two lowest-energy forms of the four possible conformational isomers obtained by rotating the C(3)=C( 4) and C(lO)=C( 11) segments through the cycloundecadiene ring.

The deep-blue colour arises from the intense 'IT*+n transition of the nitroso group at ca. 670 nm, and if either form of the solid is irradiated with red light then it is bleached, photolysis takes place, nitrogen, nitric oxide and nitrogen dioxide are evolved, and eventually white solids and a viscous yellow liquid are obtained, [3], [4]. Several nitroxide radicals and a number of diamagnetic products are formed in the photochemical reaction. The order in which they appear, and their relative abundances, depends on the length of time for which the solid is irradiated. Single-crystal e.p.r. studies, [5], [6], identify and establish the mechanism of formation of the first radical produced: it is a mono-alkyl nitroxide (2). Polycrystalline e.p.r. spectra enable the growth and decay of nitroxide radicals produced in the photolysis to be monitored, [4]: the final stable nitroxide is (3). High resolution n.m.r. spectroscopy reveals, [3], [4], the presence of the following compounds in the diamagnetic photolysis products: dinitrohumulene (4); 1,4, 4-trimethyl-8-methylene-9-nitrocycloundeca-l, 5diene (5); isomers (6) and (7) of compound (5), and in the case of the platelet form, caryophyllene derivatives. The combination of chemical and spectroscopic evidence shows that the steps in the solid photolysis reaction are as shown in the following scheme.

170

(I)

I;·)

~l

Me. [

~""J

+"'10

(Ae )

----------------

I ' 1 v "M~ NO

M~

&

Mt.

[1] [2] [3] [4] [5] [6]

M~ I"\C. Mf.

0

~

(b} _________ _ (?)____

_

O.K. MacAlpine, A.L. Porte and G.A. Sim, J. Chem. Soc., Perkin I, 1982, 1385. Z.F. Khan, O.K. MacAlpine, A.L. Porte and G.A. Sim, J. Chern. Soc., Perkin II, 1983, 1259. O.K. MacAlpine, A.L. Porte and G.A. Sim, J. Chern. Soc., Perkin I, 1981, 999. O.K. MacAlpine, A.L. Porte and G.A. Sim, J. Chern. Soc., Perkin I, 1981, 2533. Z.F. Khan and A.L. Porte, J. Chem. Soc., Perkin II, 1989, 1599. Z.F. Khan, A.L. Porte and J.E. Schubert, J. Chern. Soc., Perkin II, 1989, 1605.

171

NOVEL COUPLING MECHANISM IN SPIN-WAVE INSTABILITIES G. Wiese, H. Benner Technische Hochschule Darmstadt, Institut fur Festkorperphysik, Hochschulstr. 6 D-6100 Darmstadt, Fed. Rep. of Germany ABSTRACT - The very complex multistable behaviour observed in YIG spheres above the first-order Suhl threshold can be explained by a new mechanism which results in much stronger interactions between the excited spin-waves than conventional fourmagnon processes. PACS numbers: 75.30D, 05.45, 76.50 INTRODUCTION - High power FMR experiments on YIG spheres within the coincidence regime of the first-order Suhl instability (1.8 - 3.4GHz) differ from other experiments by a pronounced multistable behaviour accompanied by low-frequency auto-oscillations, bifurcations, intermittency and chaos [1,2]. According to Suhl, the relevant nonlinearities arise from the decay of the externally driven uniform mode

(wo = wp) into a pair of spin-waves at half the pumping frequency (Wk = wp /2), which can be described in terms of three-magnon processes [3]. For increasing excitation, mutual interactions between the excited spin-waves, which are described by fourmagnon processes, become important. We found that a new mechanism based on the indirect excitation of inhomogeneous modes results in much stronger interactions between the excited spin-waves than conventional four-magnon processes and accounts for the observed phenomena. MODEL - Inhomogeneous longwave modes with eigenfrequencies close to

Wp,

which

cannot be directly driven by the microwave field h cos wpt, can be indirectly excited by parametrically pumped spin-waves at Wp/2. In spherical samples the magnetostatic (4,3,0) mode supports such a process since it is nearly exactly degenerate with the uniform mode (d. Fig. 1). The decay of the uniform mode and the indirect excitation of the (4,3,0) mode is described by the Hamiltonian [2]:

Here co,

C430

and

c~

are the amplitudes of the uniform mode, the (4,3,0) mode and the

172

inhomogenous modes at half pumping frequency. mo and m" denote the magnetization fields of the respective modes. H~il .. ] is an integral operator generating the dipolar field of the mode in brackets. (T ",,' is defined by analogy with PIC,,' replacing mo by m430' In contrast' to previous works, instead of spin-waves we use the correct eigenmodes m"taking into account the particular shape of the sample. Thus, the usual planar spin-waves labeled by (k, Ok, IPk) are replaced by spherical spin-waves iabeled by (k, Ok, m), which are classified according to the rotational symmetry of the problem. m corresponds to an angular-momentum quantum number [2]. At the threshold the uniform mode (m=l) decays into a pair (m, m') of these novel modes (d. Fig. 1), where angular-momentum is conserved: 1 = m + m'. Generally, the pair becoming first excited at the threshold corresponds to large angular-momenta m and m'. A similar selection rule can be derived for the indirect excitation of the (4,3,0) mode (m= 3): m+ m'= 3 (cf. Fig. 1). This indirect excitation results in additional couplings between the different pairs of modes at wp/2. Using realistic estimates for the coupling constants (T ",,' and p",,', we found that such indirect couplings are roughly 300 times stronger than conventional four-magnon processes. CONCLUSIONS - We could show by numerical simulations that this novel mechanism accounts for most of the specific effects, especially for the pronounced multistability, observed in FMR experiments within the coincidence regime [2].

W Fig. 1 - Indirect excitation of the (4,3,0) mode (W430) through spherical spin-waves (mi', m2) at half pumping frequency, which are parametrically excited by the uniform

WL.30

°mm ,'" 2

mode (wo).

Pm,rn;

~

~

2

. . L,

m, m; \m mi -,2

m1 + m;= 1

-\

m2+

=

"

.. -z

ffi:.=

m~+ m 2 3 REFERENCES 1 H. Benner, F. Rodelsperger, G. Wiese: this conference 2 G. Wiese, H. Benner: Z. Phys. B 79, 119 (1990) 3 P.H. Bryant, C.D. Jeffries: Phys. Rev. A 38,4223 (1988)

173

ODMR STUDIES OF PROTEIN-NUCLEIC ACID INTERACTIONS D.H.H. Tsao and A.H. MaId Department of Chemistry University of California Davis, CA 95616, U.S.A. ABSTRACT ODMR and phosphorescence measurements on complexes of~ single-stranded DNA binding proteins bearing specific tryptophan (W) ~ phenylalanine mutations with singlestranded poly(dT) and poly(2-thiouracil) have been made. They demonstrate that close-range interactions of W40 and W54 occur with the bases of the polynucleotide. At least in the case ofW54 in the poly(dT) complex, an aromatic stacking interaction involving charge-transfer appears to occur. INTRODUCTION The interactions between proteins and nucleic acids are vital to all cellular processes. Helix destabilizing proteins, such as the single-stranded DNA binding protein from ~ W£2 SSB) are required for DNA replication, as well as for some recombination and repair processes . 1). Optical detection of triplet state magnetic resonance (ODMR) spectroscopy when applied to the amino acid tryptophan (Trp) makes possible the detailed evaluation of the involvement of these aromatic residues in stacking interactions which are thought to contribute to the stability of ~ SSB complexes with single-stranded DNA (ssDNA). Earlier ODMR work on several mutated Em SSB's in which specific Trp ~ phenylalamine (W ~ F) substitutions have been introduced has enabled us to identify those Trp residues which are stacked, and those which are not stacked in complexes with ssDNA 2). This work. which employed heavy atom-derivatized polynucleo-tides, poly(5-BrU) and poly(5-HgU}, relied on the external heavy atom effect induced in specific Trp residues as a result of aromatic stacking. Of the four Trp residues of ~ SSB which are found at positions 40, 54, 88, and 135, only residues 40 and 54 were observed to undergo stacking interactions with the DNA bases. EXPERIMENT AL Phosphorescence and ODMR measurements were carried out on the following mutated Em SSB proteins: W4OF, W54F, W88F, and the double mutant W88, 135F (prepared by Dr. J.W. Chase, Case Western Reserve University, Cleveland, OH, U.S.A., using site-directed oligonucleotide mutagenesis). Complexes were formed with single-stranded poly(dT) and with the single-stranded form of poly (sZU) and investigated by ODMR spectroscopy at pumped liquid He temperature 3). Individual sublevel kinetics of the stacked Trp residues, were determined by the MIDP method 4), using optical selection in the case of the poly(dT) complex and T ~ T energy transfer from 3(s2U) in the case of the poly(s2U) complex. The zero field splitting parameters of the stacked Trp residues were obtained by slow-passage ODMR measurements, and compared with those of unstacked Trp. RESULTS (A) polyCdD complexes: Emission from W40 and W54 could be isolated by optical selection methods using the doubly mutated Em SSB, W88, 135F. Their properties were found to differ considerably (Table), although both are believed (previous work) to stack with thymine. W54 undergoes ago 5 nm red shift when complexed with poly(dT); W40 is not noticeably shifted. (B) J2Q.lm2U) complexes: Excitation of TIE- So of s2U at A. =365 nm in complexes of poly(s2U) with ~ SSB W54F, and W4OF, produced (in addition to the short-lived s~U phosphorescence) long-lived (g. 5 s) phosphorescence from W40 and W54, respectively. These are sensitized by T ~ T transfer from poly(s2U). Sublevel lifetimes were obtained from

174

MIDP measurements while ZFS were obtained from delayed slow passage measurements. The data are summarized in the Table. TABLE E(GHz)

'tx(S-I)

'ty (s-1 )

1:z (S-I)

3.03 2.70

1.29 1.10

0.45 0.32

0.08 0.11

0.04 0.08

poly(dT):SSB poly(s2lJ):SSB

2.75 2.64

1.18 1.11

1.18 0.33

0.08 0.12

0.06 0.09

SSB(W88,135F)a RNAseTl

2.99 2.99

1.26 1.24

0.26

0.08

0.05

YMQ

poly(dT):SSB poly(s2lJ):SSB ~

D(GHz)

a W40 and W54 are unresolved. DISCUSSION Tryptophans 40 and 54 of E£2 SSB are known to undergo close-range interactions with bases of heavy atom-derivatized ssDNA 2). The measurements ofpoly(dT) complexes reveal that W40 and W54 behave differently. D and E ofW54 (but not W4O) are reduced significantly. Also, the T 1 lifetime ofW54 is drastically reduced (but only that of the Tx sublevel), while the T 1 lifetime of W 40 undergoes a smaller but significant reduction. The phosphorescence O,O-band of only W54 is red-shifted upon complex formation with poly(dT). Upon complex formation with poly(s2lJ), there is only a small reduction of the T 1 lifetimes of W 40 and W54, but a significant reduction in D and E is found and the phosphorescence is red-shifted by 3-4 nm. CONCLUSIONS These measurements confirm that W40 and W54 ofEco SSB undergo close-range interactions with the bases in complexes with poly(dT) and poly(s2lJ. The phosphorescence red-shift, ZFS reduction, and Tllifetime reduction ofW54 in the poly(dT) complex is consistent with a stacking interaction involving charge transfer between Trp and thymine 5). The smaller magnitude of these effects on W40 probably indicates a different relative orientation which is less favorable for charge transfer. The smaller effects on the lifetime found for both W40 and W54 in the poly(s2lJ) complex suggests that charge transfer may not be as important as in the complex with poly(dT). The reduction in the ZFS and the phosphorescence red-shift is due, in this case, most probably to the large polarizability of the sulfur atom of the s2U base. I) 2) 3) 4) 5)

J.W. Chase and K.R. Williams. Ann. Rev. Biochern. 55, 103, 1986. M.1. Khamis, J.R. Casas-Finet, A.H. MaId, J.B. Murphy, and J.W. Chase. J. BioI. Chern. 262, 10938, 1987. R.H. Clarke, ed Triplet State ODMR Spectroscopy, Wiley-Interscience, New York, 1982. J. Schmidt, W.S. Veeman, and J.H. vander Waals. Chern. Phys. Lett. 4, 341, 1969. D.Schweitzer, K.H. Hausser, V. Taglieber, and H.A. Staab. Chern. Phys. 14, 183, 1976.

175

ENDOR-STUDIES OF P;S5 IN REACTION CENTER SINGLE CRYSTALS OF Rb. sphaeroides R-26 AT SO C F. Lendzian 1 • B. Endeward 1 • M. Plat01 • K. Ml:Sbiusl, and W. Lubitz2. 1

Institut fUr Experimentalphysik. Freie Universitlit Berlin. D-1000 Berlin 33

2 Physikalisches Institut. Universitlit Stuttgart. D-7000 Stuttgart 80

ABSTRACT:

Anisotropic hyperfine interactions of P;S5 are obtained from

ENDOR experiments by rotation about the C 2 axes of reaction center (RC) single crystals of Rb. sphaeroides R-26. An assignment to individual molecular positions in P;65 is achieved by comparison with calculated dipolar HFS tensors using atomic coordinates from x-ray diffraction. 1. INTRODUCTION The electronic structure of the involved reactants plays an important role in the primary charge transfer from the excited bacteriochlorophyll a (BChl a) dimer P 865 to the electron acceptor bacteriopheophytin a in photosynthetic bacteria /1/. The singly occupied molecular orbital in P;65 has been investigated previously by ENDOR in liquid RC solutions yielding a set of isotropic hyperfine coupling constants (hfc's) /2/. For an interpretation of these data an unambiguous assignment of the hfc's to molecular positions in P~65 is required. This has been so far only partially achieved by selective deuteration experiments and by comparison with calculated isotropic hfc's using advanced molecular orbital theories 12.3/. Here we present additional information on anisotropic dipolar hyperfine interactions and assignments of P~65 obtained from ENDORI TRIPLE experiments on RC single crystals. 2. EXPERIMENTAL RC single crystals have been grown as described in /4/ and mounted into sealed quartz capillaries. The ENDOR/Special TRIPLE technique and the selfbuilt spectrometer have been described previously /2,5/. P;65 was generated by in situ illumination between 830 and 900 nm using a tungsten lamp.

Bacteriochlorophyll ~

176

3. RESULTS AND DISCUSSION

+,

Fig. 1 shows as an example Special TRIPLE spectra of P865 for three angles of rotation about the long crystal C 2 axis (c-axis) perpendicular to the magnetic field. The line positions depend clearly on the rotation angle. The Special TRIPLE rotation patterns of the lines recorded in 7.5 0 steps are compared with calculated HFS tensors of P;65 using the atomic coordinates obtained from x-ray diffraction 161 and the RHF-INDO/SP method 131 with a subsequent dipolar tensor calculation including spin densities on all valence orbitals within 10 ~ radius around the respective nucleus. Thereby the HFS tensors of the methyl groups la and Sa in the two BChl a molecules (L- and M-half) constituting P;65 could be assigned. The results show an LIM asymmetry of the spin densities of these positions in favour of the L-half in agreement with recent RHF-INDOI SP calculations of isotropic hfc's 13/. The rotation patterns of the

~

-protons

3.4 and 7,8 at rings II and IV can be used to determine the local geometry of these rings in P;S5 .

o

2

4

6 MHz

Ag. 1 Special triple spectra of P ~6S' Rotation about the long C 2 axls •. At 0 0 and 900 one of the other C 2 axes Is parallel to the magnetic field and all four RC's per unit cell ar. equivalent /4, 6/. Frequencies of the lines are one half of the respective hyperfine coupling /5/.

ACKNOWLEDGMENT: Dr. J. P. Allen and Prof. G. Feher. University of California, San Diego, are gratefully acknowledged for supplying the atomic coordinates of P865 . This work was supported by the Deutsche Forschungsgemeinschaft (SFB 337 and 312), REFERENCES

III

M. Plato, K. Mtsbius, M. E. Michel-Beyerle, M. Bixon. and J. Jortner. J. Am. Chem. Soc. 110 (1988) 7279.

121 F. Lendzian, Ph. D. Thesis, Freie UniversitlH Berlin (1982), 131 M. Plato, K. Mtsbius, W. Lubitz, J. P. Allen, and G. Feher, in Perspectives of Photosynthesis, Eds. J. Jortner and B. Pullman, Kluwer Academic Publ., The Netherlands (1990>-

141 D. Bumann, Diploma Thesis, Freie UniversiU!.t Berlin (1989>lSI K. Ml:Sbius an R. Biehl in Multiple electron resonance spectroscopy, eds. M. M. Dorio and J. H. Freed (Plenum Press, New York, 1978) 475.

161 J. P. Allen, G. Feher, T. O. Yeates, H. Komiya, and D. C. Rees. Proc. Natl. Acad. Sci. USA, 84 (1987> 5730.

177

RYDMR IN REACTION CENTERS OF PHOTOSYNTHETIC BACTERIA E. Lang, W. Lersch, R. Feickt, WJ. Coleman·, D.C. Youvan· and M.E. Michel-Beyerle lnstitut fur Physikalische WId Theoretische Chemie. TU Munchell. Lichtenhergstr. 4. 8046 Garching. FRG lMax-Planck-lnstitut fur Biochemie. 8033 Martinsried. FRG Department of Chemistry. MIT. Cambridge. Massachusetts 02139.USA INTRODUCTION AND METHOD Reaction Yield Detected Magnetic Resonance (RYDMR) has been shown to be a sensItIve technique to investigate recombination dynamics of radical ion pairs [I]. In this paper the technique is applied to the radical pair ~H- in photosynthetic reaction centers (RCs) formed within picoseconds after optical excitation of the primary donor lp· by electron transfer (ET) to a bacteriopheophytin (H). Under the condition of the RYDMR experiments further ET from H- to a secondary acceptor species is blocked (by its extraction) giving rise to a 10 ns lifetime of ~H-. Although this lifetime is too short for conventional EPR-methods, it is sufficiently long to allow hyperfine interaction to induce transitions between the initially generated singlet I(P+H-) and the triplet state 3(~H-) and to open thereby the triplet recombination channel leading to the local triplet state 3p· (Fig. I ).

PRIMARY ET

PH FIGURE 1: Kinetic scheme of the radical pair recombination The effect of applied microwaves under resonance conditions is detected as a change of the triplet or singlet product yield in time-resolved absorption spectroscopy. The RYDMR-signals are obtained through the measurement of the difference absorption ~OD(P_3p·) after 100 ns either in fixed microwave field (with respect to frequency and power) as a function of a static magnetic field (Bo-spectrum) or in a constant static magnetic field under resonance conditions and variation of the microwave power BI (Bl-spectrum). Such RYDMR-spectra offer access to dynamic and structural properties of the first stable intermediate in the ET sequence, ~H-, nanoseconds after its formation. The relevant recombination parameters, the exchange interaction ] between the unpaired electrons in the state (P+H-) and the recombination rate kT for the ET process 3(~H-)-3p· follow from the exact RYDMR-theory [2]. Nevertheless, crude qualitative conclusions on J and ~ are obtained from the position of the maximum, amplitude and linewidth of the Bl-spectrum. RESUL1$ AND DISCUSSION 1. Universality of recombination parameters The recombination parameters J and ~ as well as their temperature dependence have been determined for RCs from Rh.sphaeroides. Chloroflexus aurantiacus and Rh. capsulatus. Both Boand Bl-spectra (Fig. 2) show that the recombination parameters J and ~ are very similar. In RCs of Rh. sphaeroides and Rh. capsulaJus ] is 1l±1.5 G and by a factor of ~2 larger in Chloroflexus aur. at 300K. kT appears to be 0.45±O.15, O.3±O.05 and O.8±O.l5 for Rh. sphaeroides, Rh. capsulatus and Chloro/lexus aur. respectively. Both parameters tend to increase slightly towards lower temperatures.

178

I.Z

••••-.... .....

'3:!

. . . . . . 11 . . . . . . .

•

....-.... •

•

•

~1.0~~~~------~-L-.-.---------------------.------~

••

Qj

a. 0;:

..

01

1-

o?: o'

"0

=

Qi

a:::

0' 000

a Rb. capsulotus o z ChloroUe.us aur. • .. Rbo .phaorold •• 05

loa

'05

•

•

Zoo

Z05

loO

Microwave Field 9 1 [mT]

l05

'oC

FIGURE 2: High Temperature BI-spectra of RCs from Rbo sphaeroides. Rbo capsulatus wildtype and Chloroflexus ouro (Bo=1092-+0005 mT) 2.

Recombination parameters probing structure and energetics of P+H- after mutagenesis RYDMR experiments showed that single-site mutagenesis of the tryptophan M250 in RCs of Rbocapsulatus did neither affect I nor Ivr. This holds for replacement of the large aromatic tryptophan by smaller amino acid residues as the aromatic phenylalanin, the aliphatic leucin and even the polar glutamic acid (the latter leading to a 100 cm- 1 red shift of the Q,. absorption band of H). Consequently, any changes in the kinetics (as observed in the ET rate between Hand the quinone [3D are not due to changes of structure and energetics of H. This conclusion is based on the assumption that also in RCs of Rb.capsuJatus (in analogy to R.viridis [4] and Rb.sphaeroides [5]) tryptophan M250 is in van-der-Waals contact with H. From the absolute value of the rate lvr and its activationless nature folIows the electronic coupling VT ~ I cm- 1 between P+H- and 3p· [6]. It is the trademark of the RC that this coupling is by a factor of ~20 smalIer than the coupling important for the primary ET on the picosecond time scale. Conclusions from recombination parameters on the mechanism of the primary ET are possible after direct picosecond spectroscopy has identified the role of the bacteriochiorophylI B interlocated between P and H. In a 2-step sequential mechanism lp· leads to P+H- via· the kinetic intermediate P+B- whereas P+B- acts as a superexchange mediator in the I -step mechanism. A sequential mechanism would be consistent with the small values of I and VT without any further assumptions. In the case of superexchange mediated primary ET, however, the small value of VT is due to structural relaxation of P+H- following primary ET

[7].

References I. Lersch, W. (1987) Ph.D. Thesis, TU Munchen. 2. Lersch, W. and Michel-Beyerle, M.E. (1989) in Advanced EPR in Biology and Biochemsitry (AJ. Hoff, ed.) Elsevier, Amsterdam. 3. Coleman,W.I., Youvan, D.C., Aumeier, W., Eberl, U., Yolk, M .• Lang, E.. Slegl. I., Heckmann, R., Lersch. W., Ogrodnik, A. and Michel-Beyerle, M.E. (1989) in Progress in Photosynthetic Research (M. BaItscheffsky, ed.) Martinus Nijhoff Pub!. 1.1.153-156. 4. Deisenhofer, I., Epp., 0., Mild, K., Huber, R. and Michel, H. (1984), J.Mol.Bio!. 180, 385-398. 5. AlIen, I.P., Feher, G., Yeates, T.O., Rees, D.C., Deisenhofer. I., Michel, H. and Huber, R. (1986), Proc.Natl.Acad.Sci. USA 83, 8589-8593; Chang, C.H.•Tiede, D., Tang, J., Smith, U., Norris, J. and Schiffer. M.(1986), FEBS Lett. 205, 82-86. 6. Bixon, M., Michel-Beyerle, M.E. and Jortner, I. (1988) IsrJ.Chem. 28, 155-168. 7. Michel-Beyerle, M.E., Bixon, M. and Jortner, I. (1988) , Chem. Phys. Lett. lSI, 188-194.

179

Spin Polarization and

Relaxation

180

OPTICAL SPIN POLARIZATION AND SPIN WAVES IN HELIUM THREE GAS G. Vermeulen and F. Laloe Departement de physique de l'ENS, 24 rue Lhomond, F 75005 Paris, France ABSTRACT We discuss some aspects of nuclear spin polarisation in helium three gas: laser optical pumping with various applications ranging from polarized targets for nuclear physics to the polarization liquid helium three; spin relaxation, in particular due to motion of the atoms in magnetic gradients or depolarization on the walls; finally, spin waves in polarized quantum gases at low temperatures, which can be detected in NMR experiments with detection coils mounted in opposition. PACS numbers: 51, 67. INTRODUCTION Nuclear magnetic resonance experiments in gaseous helium three have been done for many years. Initially, the polarization was obtained by using low temperatures and high magnetic fields. Unfortunately, this simple method is limited to relatively low polarizations (a few percent), because of field limitations and because the accessibility of low temperatures is limited to a fraction of a degree by the liquefaction of the gas. Another possibility is the method of optical pumping in helium three 1) 2) which, even at room temperature, allows one to obtain high polarizations with an equipment which is no longer complicated or very expensive. The purpose of the present contribution is to discuss various applications of this method, for example nuclear spin relaxation studies in the bulk gas phase or on walls covered by solid noble gases, or the experimental study of spin waves, a new spin mode which exists in a quantum gas at low temperatures. OPTICAL PUMPING When A. Kastler invented optical pumping in 1950 , despite the fundamental interest of helium as a simple atom, nobody thought of trying optical pumping in helium, because the resonance frequency is too far in the ultraviolet. Moreover, because the coupling to an optical wave is primarily to the electrons, one needs large hyperfine coupling to transfer the orientation to the nuclear spins, which does not occur in singlet helium. These difficulties were solved in 1963 by the indirect optical pumping method invented by Colegrove et al. 1), who used a metastable state of the atom as an intermediate level, where the polarization is created by a near infrared radiation 1.081-'), and from which the polarization is transferred to the ground state by collisions. A limitation of the method was neverteheless the unsufficient intensity of discharge lamps providing radiation at ..\ = 1.08 1-'. A very natural idea was then to use lasers, but for many years no cw laser was available at the right wavelength. It took several years of efforts to M. Leduc and her coworkers at the ENS to develop an adequate instrument. These efforts have now converged towards simple technical solutions 3), and convenient and powerful arc lamp pumped LNA lasers are presently available and give access to polarizations exceeding 60% . Many applications of helium optical pumping have been demonstrated years ago by G.K Walters, L.D. Schearer and coworkers: polarized target for nuclear physics, extraction of beams of polarized ions or electrons, spectroscopy of excited states, etc.; for more detail, see the references listed in 2). Because the experiments can now be done in much better conditions with the lasers, several groups in the world are building highly polarized targets to be inserted in accelerators. The line followed by our group at the ENS is the study the quantum properties of spinpolarized helium three at low temperatures, e.g. transport in the gas phase which becomes more efficient when the gas is polarized because of quantum statistical effects 2) 4). Another possibility is to produce highly polarized helium three liquid from an optically oriented gas, an idea which is not new 5). If the liquefaction occurs in a time short compared to the relaxation time of the spins, practically all of the polarization is transferred from the gas to the liquid. A few years ago, our

(..\ =

181

group resumed this line of research in order to demonstrate that good polarizations could indeed be obtained in this way 6); polarisations reaching 50% are indeed accessible in a liquid at about 500 mK. One of the purposes of an experiment in progress in our group is the study of the non-trivial role of the nuclear polarization in the diagrams of liquid-gas equilibrium. We are also planning to reach lower temperatures and to create degenerate polarized liquid, which raises several exciting theoretical questions 7). RELAXATION One source of relaxation is magnetic field gradients which, because the constant motion of the atoms in the gas, act as a time-dependent perturbation which can flip their spins. In fact, this process can also be seen as an interesting tool to study both the slow diffusion motion ot the atoms and their fast motion between collisions (see references given in 8). A convenient NMR technique is to make use of strongly inhomogeneous radiofrequency fields; accurate values of the spin diffusion coefficient in helium three gas were obtained in this way 9). Another relaxation process is collisions on the walls wich contain unavoidable megnetic impurities. Its efficiency varies exponentially with the ratio between the binding energy of the atom on the walls and the temperature: clearly, at low temperatures, one has to reduce the binding energy as much as possible. This was done by covering the walls by various "cryogenic coatings" such as solid Hydrogen or Neon. From this V. Lefevre-Seguin was able to perform a series of measurements of absorption energies of helium on various substrates 9). SPIN WAVES In a classical gas there is only one propagating mode: sound waves (ref. 10 discusses the effect of nuclear polarization on this mode); phenomena such as viscosity or spin diffusion are purely damped. It was thought until a few years ago that the high randomness of atomic positions and collisions in a gas would prevent any spin oscillation mode to propagate (as they do in condensed systems). The existence of spin waves in gases was nevertheless predicted by E.P Bashkin 11) and our group 12). The microscopic phenomenon at the origin of the collective modes is a quantum indistinguishability effect occuring during binary collisions, the "identical spin rotation effect". Experiments have been done in various quantum gases (spin polarized Hydrogen and Helium). At Cornell University for example, a combination of suitable gradients of magnetization and fields lead to beautiful NMR spectra showing the existence of spin wave modes 13). At the ENS, we used a method with pickup coils mounted in opposition 14); then, the NMR signal is not sensitive to the total magnetization of the sample, but only to the spin wave modes. REFERENCES 1) F.D. Colegrove, L.D Schearer and G.K. Walters, Phys. Rev. 132,2561 (1963). 2) M. Leduc and D.S. Betts, Ann. Phys. 11, 267 (1986). 3) C.G. Aminoff, C. Larat, M. Leduc and F. Laloe, Rev. Phys. Appl. 24,827 (1989) 4) C. Lhuillier and F. Laloe, J. Physique 40, 239 (1979); 43, 197 and 225 (1982). 5) H.H. Me Adams and G.K Walters, Phys. Rev. 18,436 (1967). 6) G. Tastevin, P.J. Nacher, 1. Wiesenfeld, M. Leduc et F. Laloe, J. Phys. 49, 1 (1988). 7) A.E. Meyerovich, chap. 14 of "Helium Three", W. Halperin ed., North Holland (1990). 8) V. Lefevre-Seguin, P.J. Nacher and F. Laloe, J. Physique 43,737 (1982). 9) (a) R. Barbe, M. Leduc et F. Laloe, J. Physique, 35,699 and 935 (1974). (b) M. Himbert, J. Dupont-Roc and C. Lhuillier, Phys. Rev. A 39, 6170 (1989). 12) V. Lefevre-Seguin et al. J. Physique 46, 1145 (1985). 10) G. Vermeulen, M. Elbel and F. Laloe, A. Phys. D, 15, 13 (1990). 11) E.P. Bashkin, Pis'ma Zh. Eksp. Teor. Fiz. 33, 11 (1981). 13) B.R. Johnson et al. Phys. Rev. Lett. 52, 1508 (1984). 14) G. Tastevin, P.J. Nacher M. Leduc and F. Laloe, J. Physique Lett. 46, L-229 «1985).

182

CHEMICAL EXCHANGE AND QUANTUM EXCHANGE Narayanan D. Kurur, Daniel H. Jones, and Daniel P. Weitekamp Arthur Amos Noyes Laboratory of Chemical Physics, 127-72 California Institute of Technology, Pasadena CA 91125, U.S.A. ABSTRACT The mutual chemical exchange rate has been derived with the rovibrational lattice treated quantum-mechanically. Our formulation contrasts sharply with previous descriptions of the role of tunnelling in NMR lineshapes. PACS numbers: 05.40.+j, 33.25.Bn, 67.90.+z, 76.60.Es INTRODUCTION The concept of chemical exchange is universally used in the simulation of temperature-dependent NMR lineshapes. Its conceptual basis includes the notions of discrete molecular configurations and transition state theory. Recently we pointed out that this \>icture of molecular structure is inadequate for a variety of metal polyhydrides (1,2). These molecules exhibit large temperature-dependent proton-proton scalar couplings in solution which are now understood to be tunnel splittings of the sort previously studied in quantum solids. Since the earliest NMR work on cyclic exchange in methyl groups, it has been recognized that tunnelling may appear both in the unitary dynamics as a scalar coupling and as a mechanism for irreversible dephasing, but diverse quantitative relationships have been proposed for the relationship between these effects. The issues can be illuminated with a mechanical analogy in which the spin system is replaced by an oscillating pendulum. Imagine an ensemble of pendulums which at t = 0 have the same length and are set in motion with the same phase. Each pendulum is controlled by a Maxwell demon, who at random intervals changes the length (and thus the frequency) in discrete steps. Averaged over long times all of the pendulums will have the same mean frequency, since we assume that with each length there is associated an energy drawn from the same Boltzmann distribution. However, the random manner in which a given pendulum samples these lengths will cause the ensemble to become incoherent. The rate of this dephasing will depend on both the distribution of lengths and the rate of switching between them. The proton tunnelling in the metal trihydrides has been shown to be pairwise exchange between inequivalent sites (1,2). Thus, consider a system consisting of two spins occupying two sites in a molecule which is rapidly sampling many thermally accessible rovibrational manifolds (the pendulum lengths) indexed by n. The scalar coupling will split the singlet and triplet nuclear spin states in each manifold by tUn (the instantaneous pendulum frequencies) around their center energy, which is dominated by rovibrational contributions. These eigenvalues are found by solving a spatial Schrodinger equation for the nuclei. If the two nuclei are of the same isotopic species, the potential energy for this calculation necessarily has two equivalent minima separated by a barrier. For states below this barrier, the splittings tUn are referred to as tunnel splittings. They increase in magnitude with energy, becoming comparable to the rovibrational splittings near the barrier.

183

RESULTS AND DISCUSSION describing the coupled system of For a given model system Hamiltonian spins and rovibrational degrees of freedom, there is an equilibrium density operator Peq(T). Because the rovibrational relaxation is fast compared to the time scale of

"%,

the NMR transient, there is a well~efined spin Hamiltonian tN= Trn(Peq ,,%) which determines the unitary evolution of the spin system. The superscript n denotes a restricted trace operation which projects out the spatially-averaged spin Hamiltonian in a manner consistent with the symmetrization postulate. This generalizes the idea of Boltzmann-weighted average tunnel splittings (the mean pendulum frequency), which has been used previously to describe the temperature dependence of the scalar coupling for both methyl and trihydride protons. The next step is to calculate the NMR lineshape that results from this rapid rovibrational relaxation. Bloch-Wangsness-Redfield relaxation theory has been applied to show that the chemical exchange rate (the pendulum dephasing rate), which is usually introduced phenomenologically, has a microscopic description reminiscent of other transport coefficients, including the well-known NMR relaxation times. Specifically, we show that the chemical exchange rate is

kJ = fooo( 200 mG) . At X-band and Q-band frequencies, the g-anisotropy of the P70 0 + radical of photo system I cannot be measured due to the dominant unresolved hyperfine broadening. Our measurements with increased g-resolution are able to separate different components. The signal from P700+ radical shows a slightly asymmetric line. Unresolved hyperfine interactions still dominate the linewidth, but preliminary analysis suggest an upper limit for the g-anisotropy of llg ~ 10- 4 , which is smaller than llg values deducted from orientation dependent measurements on single crystals of bacterial reaction center. 5 CONCLUSION Despite the complications with microwave sources and components for millimeter wavelengths, the results of our experiments indicate that high frequency ESR and DNP are promising methods for enhancing resolution and sensitivity. We report here the first DNP measurement on a powder sample at room temperature for frequencies above 100 GHz. ESR measurements on photosystem I show the improved spectral resolution at higher magnetic fields. REFERENCES 1. H. Brunner, K. H. Hausser, H. J. Keller, D. Schweitzer Solid State Comm. ~, 107 (1984) 2. W. Stocklein, H. Seidel, D. Singel, R. D. Kendrick, C. S. Yannoni Chern. Phys. Lett. ~, 277 (1987) 3. O. Ya. Grinberg, A. A. Dubinskii, Ya. S. Lebedev Russ. Chern. Rev. ~, 850 (1983) 4. R. A. Wind, H. Lock, M. Mehring, Chern. Phys. Lett. ~, 283 (1987) 5. J. P. Allen, G. Feher, Proc. Natl. Acad. Sci. USA al, 4795 (1984)

188

WEAK FIELD RADICALS.

DYNAMIC

NUCLEAR

POLARIZATION

WITH

PHOSPHORUS

Ayant Y.; Kernevez N.; Secourgeon L.; LETI-CENG, 85X,38041 Grenoble France Tordo P.; L.S.R.E.P., Univ. de Provence, 13397 Marseille Cedex 13 France Introduction

Dynamic Nuclear Polarization (1) is quite useful for NMR earth field magnetometer(2) whose sensitivity increases with the DNP factor. The interest of free radicals is due to the hyperfine structure which induces an important separation of the electron energy levels at weak fields and increases thereby the DNP factor. The DNP between solvents protons and nitroxide radicals is well known (3) . We describe in this paper DNP calculation and measurements on phosphorus radicals which present a more important hyperfine structure. Ca1cu1ation

The evaluation of the DNP efficiency requires first to calculate the radical energy levels structure at earth field and then to determine the frequency and the intensity of the allowed transitions. The static hamiltonian Ho involves an electronic Zeeman effect term and an hyperfine coupling term.We neglect the nuclear Zeeman term. Ho = - 1 h Bo.S + L Ai Ii.S i

where Bo is the static field, S tne electron spin, Ii and Ai are the spin and the hyperfine constant of the nucleus i coupled with the electron. The coupled nuclear spins and the value of the hyperfine constant are determined by X-band ESR spectrometry. We have studied two types of phosphorus radicals: -nitroxide phosphorus radicals for which the electron is coupled with nitrogen and phosphorus nuclei, -a phosphorus centered radical for which the electron is coupled with the phosphorus nucleus and two radical proton. The figure 1 presents the earth field energy spectrum of a nitroxide phosphorus radical. Two transitions are intense. It's interesting to note that the relative sign of the nitrogen (An) and phosphorus (Ap) coupling are not determined by high field but the low field structure depends on it. The figure 1 corresponds to same sign constants. The figure 2 presents the phosphorus centered radical energy levels.The number of levels is to ,ive an efficient DNP. Experimenta1

resu1ts

We have developped an earth field DNP magnetometer. The solvent proton resonance circuits at 2 KHz are oriented in the Bloch positions. The high frequency resonator, tunable from 50 to 300 MHz, allows the electron resonance. The frequency of the measured transitions (figure 3) co'rresponds to the calculation. The earth field DNP measurement

189

proves that the nitrogen and phosphorus constants have the same sign. The DNP factor is about 2000. The signal measured on the phosphorus centered radical is very weak as shown in figure 4 because the DNP factor is greatly decreased by the paras it coupling with the protons as predicted. Concl.usion Our earth field DNP spectrometer gives accurate measurements on phosphorus radicals in agreement with calculation. ,"r

-~'~.'----_~~~~':: air

E4,

21

K=l F=2

~~

1

•

1.3

fDt&

II_J .,

·1

1,26 M!iz

• t 1

O.7J .lIb

·1

K=l F=l

1

K=l F=O

0,95 MIl:

0_ 1

0

279

174 MIl:

MH:

t 0,34

K-o F=l

0.01 taU.

MIl:

figure 1:" Earth field energy levels of a nitroxide phosphorus radicaL

D.N .. P. signal

Figure 2 : Earth field levels of a phosphorus centered radical.

D.N.P. signal

( .. Veff)

( .. Verr)

171,5 MHz

175,4 MHz.

/\f\ l

170

Figure 3

I

I

•

17S

~HF(MHZ)

D.N.f. lines measured with a nitroxide phosphorus radicaL

.~---. 270

280

Figure 4 : D. N. P. lines .. easured with the phosphorus centered radicaL

References (1) Abragam A.,The principles of nuclear Magnetism;Clarendon Press,Oxford 1961 (2) Salvi A., Rev. Phys. Ap. 1970 (5) 131 (3) Ayant Y., Besson R., Casa1egno R., J. Physique 41 (1980) 1183-1192

190

NMR-INVESTIGATIONS OF HOMOGENEOUS HYDROGENATION REACTIONS USING PARA HYDROGEN

J. Bargon, J. Kandels, P. Kating, A. Thomas, K. Woelk Universitat Bonn, Institut fiir Physikalische Chemie, \Vegelerstra13e 12 5300 Bonn 1, Fed. Rep. of Germany

ABSTRACT Homogeneous hydrogenations with or tho- or para-enriched hydrogen result in strongly enhanced IH-NMR-polarization signals due to symmetry breaking during the reactions. Polarization is observed only, if the transferred atoms stem from the same molecule ("pair correlation"). The polarization pattern reflects the reaction path, e.g. the reaction of two different educts leading to the same product shows different polarization spectra. Examples given include hydrogenation of certain alkines to alkenes as well as alkenes to alkanes using organometallic rhodium catalysts. INTRODUCTION Para-enriched (p-H 2) and ortho-enriched H2 (o-H2) instead of normal H2 (25% P-H2 and 75% o-H 2) is used for homogeneously catalyzed hydrogenations. The IH-NMR spectra of the reaction products show strongly enhanced polarization patterns due to the break of exchange symmetry of the H2 through the reaction 1). Examples given demonstrate this effect and lead to qualitati....e discussions about the reaction mechanism. RESULTS The transition metal complex [Rh(NBD)(PPh3)2]+PF6" (NBD

= 2,5-norbornadiene)

is hydrogenated using p-H 2. The resulting polarization pattern after 15s indicates the production of 2-norbornene (Fig.la). After 45s this reaction is completed. The 2-norbornene concentration is too low to be detected by regular NMR (after relaxation of the 2-norbornene spin states). Addition of NBD and further hydrogenation using P-H2 result in almost identical polarization patterns of the 2-norbornene (Fig.lb). After NBD has reacted completely, the 2-norbornene is hydrogenated to norbornane using P-H2 (Fig.lc). Other experiments using 2-norbornene as the sole educt together with [Rh(NBD)(PPh3 hl+PF as well as with Wilkinson's catalyst confirm the formation of 2-norbornene. The individual polarization patterns depend characteristically on the position of the transferred hydrogen atoms in the product. This is confirmed using two different educts (2,5-dihydrofuran or 2,3-dihydrofuran) leading to the same product (tetrahydrofuran).

s

EXPERIMENTALS The P-H2 used in the experiments aboye was enriched using a charcoal cell held at liquid nitrogen. A continuous stream of P-H2 is available at a pressure of about 1.2bar. This stream is bubbled through the NMR-probe via a capillary for a few seconds. After tenninating the P-H2 stream the NMR-pulse is set and the polarization spectrum is obtained. This can be done repetitively, and accumulation of spectra is possible. Kinetic studies using a pressure controlled apparatus for the P-H2 injection are in progress.

191

Using o-H 2 instead of P-H2 results in inverted polarization spectra, i.e. emission and absorption signals are interchanged 2). Due to the threefold spin-degeneracy of o-H 2 the signals are weaker by a factor of 3.

CONCLUSIONS The results of Fig.1 confirm the mechanism postulated by Schrock and Osborne 3): hydrogenation and loss of the NBD ligand of the catalyst precursor [Rh(NBD)(PPh3 )2]+PF6" lead to a catalytically active species, which hydrogenates selectively NBD to 2-norbornene. Furthermore, the catalyst precursor is a possible intermediate in the catalytic cycle itself. The 2-norbornene formed in the course of this reaction is subsequently hydrogenated to norbornane. This example demonstrates the usefulness of this method. The experiments starting from two different dihydrofurans prove the so called "pair correlation": the spin information of the inserted H2 is transferred to the reaction product, and the resulting polarization pattern depends on the individual positions of the transferred H-atoms. c

(e)

-~A--~

__

....,.I\,-"V

r\clc

+P-~ (Cal.)

lJ:)

+p-~

((\')

l!..J)

(Cat.)

Figure 1: IH-FT-NMR-spectra of the hydrogenations using [Rh(NBD)L 2]+PF; as catalyst precursor, NBD = 2,S-norbornadiene, PPh3 , Cat. catalytically active speL cies. (a): [Rh(NBD)L2]+PF; (6.1mg) dissolved in Iml acetone-d s after hydrogenation with para-enriched H2 (P-H2) for 15s. (b): After addition of NBD (8.5mg) and hydrogenation with P-H2 for 15s; this polarization pattern is observed for about 12min. (c): 150s after the 2-norbornene signals disappear, norbornane signals appear showing polarization as well.

=

=

--

(a) - - f - - - - - - . /

[Rh((j))L 2 t

~~::

~A B

PPM'I'I i iii iii

7

6

Iii

5

II

Iii I'I I,

J

iii

'I'

Iii

I'

i "1111

210

REFERENCES 1) C. R. Bowers, D. P. Weitekamp, Phys.Rev.Lett. 57, 2645-8 (1986). 2) J. Bargon, J. Kandels, K. Woelk, Angew. Chern. Int. Ed. Engl. 29,58-9 (1990). 3) R. R. Schrock, J. A. Osborn, J.Am.Chem.Soc. 98,2134-43,2143-7,4450-5 (1976).

192

ODENDOR OF F-CENTRES WITHOUT MICROWAVES AND THALLIUM IMPURITY NMR IN KC1:Tl DETECTED WITH THE MCDA TECHNIQUE

N.G.Romanov+ , O.M.Hofman, and J.M.Spaeth

Universitaet-GH-Paderborn, FB-6 Physik, Warburger Str. 100, D-4790 Paderborn, F.R.G. + ~.F.Ioffe Physico-Technical Institute, Academy of Sciences of the USSR, 194021 Leningrad, USSR

ABSTRACT By monitoring magnetic circular dichroism of the absorption (MCDA) of Fcentres in KC1:Tl crystals optically detected electron-nuclear double resonance (ODENDOR) of F-centre neighbours could be detected without microwaves. In addition, thallium impurity NMR Signals were observed with the opposite sign. INTRODUCTION EPR and ENDOR detected via MCDA of optically pumped F-centres in alkali halides were measured in Ref. 1) to study their ground and relaxed excited state. An influence of hyperfine interactions on the optical pumping cycle of Fcentres was analyzed in 2). F-centre ENDOR spectra of the ground state were recorded without microwaves using the luminescence of "close" 3) and "distant" 4) F-centre pairs. In this note we report on the observation of F-centre ENDOR without microwaves under different experimental conditions and also on the observation of thallium impurity NMR by monitoring the MCDA of F-centres in thallium doped KC1. RESULTS AND DISCUSSION KCl crystals doped with thallium (about O. S mol. %) were irradiated with the X-rays at room temperature. F-centres and several Tl-related centres were produced in the crystals I 5) I. By monitoring MCDA of F-centres in the irradiated KCl:Tl at loS K we observed resonance signals which were due to a cross-relaxation of F-centres with Tl 2+, Tlo(l) lor, AF(Tl)1 and other centres. The light which was used to monitor MCDA produced optical pumping of F-centres and made it possible to observe the cross-relaxation effects I 6)/. Additional application of a radiofrequency field resulted in two types of resonance effects: a) The MCDA increased by 0.25 to O. S % at values of the radiofrequency which corresponded to the ENDOR frequencies of the first and second shells of Fcentre neighbours and also to the 3SCl and 37 Cl distant ENDOR signals. The relaxation time of these ODENDOR signals was about 1 sec. b) The MCDA de~reased by about 1.S % at values of the radiofrequency which corresponded to the Z03Tl and 20STl NMR frequencies. These signals were observed at any magnetic field between 1 and 3 Tesla and their relaxation time was about 180 sec. The fact that the observation of the thallium NMR was connected with the MCDA of F-centres and not with that of other centres was confirmed by changing the wavelength through the F-centre MCD.

193

The ODENDOR and NMR signals which were recorded by monitoring MCD of F-centres at 515 nm in magnetic field 1.8 Tesla are shown in the figure.

f

35 Cl 37 C1

L

203 T1

L

ClI!

205 Tl

Kr

::I ttl

0

CJ

::0:

6

10

14 F

18

r e q

42 u e n c y

44

46

MHz

The observed ODENDOR without microwaves is discussed in terms of optical pumping of F-centres. Possible explanations for the observation of thallium NMR. such as optical polarization of nuclei induced by a dipole-dipole hyperfine interaction. a spin diffusion mechanism and others are considered.

REFERENCES 1) L.F.Mollenauer. and S.Pan. Phys. Rev. B 6. 772 (1972). 2) A.Winnacker. and K.E.Mauser. B.Niessert. Z. Physik B 26. 97 (1977). 3) C.Jaccard. P.A.Schnegg. and M.Aegerter. phys. stat. sol. (b) 70. 486 (1975). 4) C.Jaccard, and M.Ecabert. phys. stat. sol. (b) 87. 407 (1978). 5) F.J.Ah1ers, F.Lohse. J.M.Spaeth. L.F.Mo1lenauer. Phys. Rev. B 28, 1249 (1983). 6) N.G.Romanov, V.V.Dyakonov. V.A.Vetrov, and P.G.Baranov, Fiz. Tverd. Tela 31, No.11, 106 (1989); Sov. Phys.-Solid State 31. No.ll (1989).

194

31p

RELAXATION MECHANISMS IN PHOSPHORUS METABOLITES

E.R. Andrew, W. S. Brey, R. Gaspar, Jr. Departments of Physics, Chemistry and Radiology, University of Florida, Gainesville, FL 32611, USA ABSTRACT Measurements have been made of the relaxation time Tl of 31p for the individual resonances of the metabolit~s AMP, ADP, ATP, Pi and PCr (phosphocreatine) in H20 and 0 20 solutions from 278 to 333K at various concentrations. The contributions of dipolar, chemical shift and spin-rotation relaxation mechanisms have been separated and activation parameters determined. PACS number: 33.25.Bn INTRODUCTION High resolution 3lp NMR spectra of metabolites obtained in vivo from humans, animals and cells provide valuable information concerning the biochemistry of living systems in normal and diseased states. For quantitation, saturation transfer, NOE, and studies of molecular mobility and exchange, relaxation knowledge is very important, but few systematic measurements have been made and no analysis of mechanisms. As a first step we have made such measurements for five principal metabolites in pure aqueous solutions. Measurements were made at 121.5MHz from 278 to 333K and also at 40.5MHz. RESULTS AND DISCUSSION Activation plots for the five metabo1ites at 121.5MHz are shown in figs. 1-5. The temperature dependence enables a discrimination to be made between the dipolar and chemica1 shift anisotropy (CSA) mechanisms and the spin-rotation mechanism. Use of 0 20 and H20 solvents assists in separating dipolar and spin-rotation contributions. The magnetic field dependence enables separation to be made between the dipolar and CSA contributions. The concentration-dependence enables a discrimination to be made between intra-and inter-molecular dipolar contributions. Relaxation due to paramagnetic contributions was minimized by careful sample preparation (1, 2). Scalar relaxation was calculated to be negligible. Some detailed results follow. Spin-rotation was only important for Pi (fig. 4), 27% in H20 at 310K, 57% in 0 20. In AMP the CSA mechanism accounted for 51% and 11% at 12l.5MHz and 40.5MHz respectively; in ADP 53% and 11% for P"" 25% and 4% for P13 ; in ATP 59% and 14% for P. and DADP .0 0 0EUTERATEO (01

t6 1

.

;::-

.00rUN-=O'-=E.:...UT;...:E:.:.;R.:..:.AT;...:E:..:.O_---, (bl

115'

AOP

';:-.

10 2

:::

DADP

,, ,, ,,

16 2

:::

I I

! i

10 3

10 3

-.

.00

-.

I

.00

.5

/

ISOK

5

'0 IITOo3j( 11

'5

Fig. 1 31p Observation of Onset of The PSG State (a)

31p

D-RADP(X=0.441

-I

T

10

en

,

I-

-2

10

10 3

16 '

T

102

20

5

25

(b) 31p

D-RADP(X=0.781

en

I~

10 3

1~0~--~5~-~10~-~15~-~2~0--725

liT (163 f(1)

Fig. 2 The (a) figure (for x = 0.44 in the middle of th PSG state) shows two T 1 minima; whereas, in (t (for x = 0.78, near the boundary of the PSG state: the low temperature T 1 minimum nearly disappean

REFERENCES 1. R. Blinc, D.C. Ailion, B. Gunther, and S. Zumer, Phys. Rev. Lett. R 2826 (1986). 2. R. Blinc, J. Dolinsek, V.H. Schmidt, and D.C. Ailion, Europhys. Lett. Q, 55 (1988). 3. S. Chen and D.C. Ailion, submitted to Phys. Rev. B (1990).

138

MAGNETIC RESONANCE OF PROBE Yb 3 + ANTIFERROMAGNETIC PHASE OF DyP0 4 .

AND

Er 3 +

IONS

IN

THE

J.M. Baker, B. Bleaney, A.A. Jenkins and P.M. Martineau Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK. ABSTRACT The contribution to the internal field at probe paramagnetic ions Yb 3+ and Er3+ set up by exchange with the host Dy3+ ions in anti ferromagnetic DyP04 has been measured by magnetic resonance. This shows clearly that the exchange cannot be modelled as isotropic exchange between the real spins of the lanthanide ions. PACS number:

7530H, 7630K

INTRODUCTION Paramagnetic resonance in neat paramagnetic salts usually has a very large line width because of inhomogeneous broadening due to interaction with many randomly oriented neighbours. For this reason EPR has usually been performed on probe paramagnetic ions as a dilute species in diamagnetic salts. Narrow lines should also be obtainable for EPR of probe paramagnetic ions in an ordered magnetic system, as the local internal field does not vary from site to site on the same sublattice. DyP0 4 becomes a two sublattice antiferromagnet below TN = 3.39K (1,2). The anisotropy is very large, so that the magnetic moments of Dy3+ are aligned along the c-axis. A probe ion with g values gil and g.J,. would experience a magnetic field Bo ± Bi' where Bo is the applied field and B. is the internal f~eld along the c-direction, the sign de~ending upon the sublattice. The resonance condition for B making an angle e with the c-axis is then: 0 (hY/Ps)2 = [gil (BoCos9 ± Bi)]2 + [g.l.BOSin9]2 (1) Hence, either by measuring B for both sublattices, or for one sublattice at two values of 0 v, one may measure both g-values and B.. One or both of the resonances may be unobservable if B exceeas the field Bs1 for spin flip. In the spin flipped stat~ all Dy3+ moments are parallel to one another and to the c-axis. However, in this state with large macroscopic magnetisation, the internal field is spatially inhomogeneous, except in ellipsoidal specimens, leading to large line width. RESULTS Measurements have been made at 1.3K on a crystal of DyP0 4 doped with 0.003 mole fraction of Yb. EPR was observed at both 35 and 24 GHz, but not at 17 GHz. The line width was about 20 mT. At some orientations of B two resonances were observed, corresponding to the two sublgttices. For one of the resonances at small values of 9, and for both resonances at 17 GHz, the field required for resonance exceeded Bst (=0. 57T for a needle shaped specimen), accounting for the lack of observed resonance. The angular variation of the resonance is in excellent agreement with equation (1) with the parameters listed in the table. The g-values for Yb 3+ are close to those for Yb 3+ in YP04 , which

199

together with the observation of characteristic hyperfine structure for 171 yb , confirms that the ion is Yb 3+. The table also lists data for a second resonance observed in the crystals due to an accidental impurity. Er is the likely impurity in DyP04 as it is close to Dy in the lanthanide group, and the g-vafues are close to those of Er3+ in YP0 4 • host DyP04 YP04 (3) DyP0 4 YP04 (4)

ion Yb 3+ Yb 3+ Er3+ Er3+

g" 1.7 1. 522 6.3 6.42

g.J,. 3.1 3.152 4.7 4.81

Bi/T 1.277

B• .IT 1.041

B.. (model) /T 0.308

0.426

0.190

0.411

DISCUSSION The internal field B. is the sum of a magnetic dipole field Bdip ' which is calculable \or the known magnetic moments in the known structure, and an exchange field Box. In DyP04 Bdi is calculated to be 0.236T, which has been used to obtain the values of B.. in the table. If exchange can be represented by the hamiltonian k(~.~') between the real electron spins ~ and ~' on the two ions, the exchange fields for a guest spin ~ and for a host spin ~' are related by B• .IB' .. = (1-g J -1)/(1-g J ,-1) (2) where gJ is the Lande g-factor. The mean of three different e s tima te s of B . from the properti e s of DyP04 ( 2 ), and the calculated dipolar field Bdi = O. 236T, gives Box' = O. 616T for Dy3+ in DyP0 4 • Then equation P (2) gives values of B for Yb 3+ and Er 3+ in the last column of the table. ex CONCLUSION The comparison of the measured and extrapolated values of B.x show that the model of isotropic exchange between real spins is not adequate to describe the exchange between lanthanide ions. REFERENCES 1) Wright & Moos, J. Appl. Phys. ~ 1244, 1970; Wright et al, Phys. Rev. ~ 843, 1971. 2) Ellis et al, J.Phys. C: Solid State Phys. ± 2937, 1971. 3) Hillmer, Stat. Phys. Sol. ±l 133, 1971. 4) Plamper. Stat. Phys. Sol. ±l 135, 1971.

200

CONTRIBUTION OF HYDROGEN BONDING (HB) TO THE LEAKAGE FACTOR IN DYNA}!IC NUCLEAR POLARIZATION (DNP) M.P. FERROUD-PLATTET, N. KERNEVEZ, Y. AYANT, LETI-CENG, 85 X 38041 Grenoble A. SALVI, ASTEC, 17 rue des Martyrs 38000 Grenoble France INTRODUCTION One particular application of DNP (1,2) between solvent protons and the electron of a free radical is its use for NMR earth field magnetometers (3), whose sensitivity increases with the DNP Factor (DPF). This factor is proportional to the so-called leakage factor f; f = 1 - Tl/TlO where Tl' TIO, are the nuclear relaxation times of the radical solution and of the pure solvent respectively. More than just leakage phenomena, f expresses the efficiency of the Abragam-Overhauser electron-proton coupling, and then we prefer to call it the "Efficiency Factor". In this paper, we describe an experimental determination of this factor and its interpretation in terms of DNP, for several M/lOOO radical solutions; perdeuterated 2,2,6,6 tetramethyl-4-piperidone 15N-oxide in CH30H, CH30D, CD 30H. RESULTS An earth field free precession equipment (4) has been elaborated (figure 1) and qualified in our weak magnetic field laboratory. We have measured Tl and TID values and calculated f for some solvents. T2 can also be determined by a phase measurement of the NMR line (figure 2) obtained by a DNP spectrometer developed for the Phosphorus radical characterization (5). Our research is focused on the study of HB effects on the efficiency factor. Methanol is one of the best solvents for our applications and it is difficult to explain the corresponding DPF without taking into account the HB contributions. Then it is interesting to compare the TI, TlO, f, and the EPR linewidth (6HEPR) of CH30H, CH30D, CD30H (table I) Solvent

Table I

Tl(s)

TlO(s)

f

T2 (s)

6~PR (G)

CH30H

2

6.5

0.69

2.18

0.38

CH30D

2.6

9

0.71

2.6

0.33

CD30H

0.83

11

0.92

0.76

0.31

DISCUSSION The HB effect is clearly shown by the factor 3 between- the Tl of CH30D and CD30H. The Tl value of the CH30H let us suggest that, in this case, an HB contribution still exists. In spite of the theoretical predictions Tl and T2 are nearly equal, even in presence of a scalar coupling through HB. If we assume that electron-proton coupling increases with HB, it comes that for CD30H the efficiency factor is drastically greater. But, because of the small number of protons per molecule and the weak value of T2 this solvent is unfortunately unexploitable for our DNP applications. The radical-solvent coupling is obviously expressed by 6HEPR' Surprisingly, the f factor and the EPR linewidth do not have the same solvent dependence. In contradiction with the theory (6), it seems that the 6HEPR decreases with the number of solvent's protons.

201

"" R LINE AMPLITUDE eYalt)

•

~

P . . . . (De.r. .

temperature

Sensor

oI

Somple

••Jectlo. colli 'or: • field 'olariz.lloD • Sign . . . . ceptlon

.5

------\-----

\

.. -----"\". . FIG_I.

Earth Field Free Precession Equipment

12-11- 9.84 nT " ' T2 .0.76 s

FIG_ 2 : NMR Line and Phase Measurement by Earth Field DNP Spectrometer

CONCLUSION The efficiency factor depends greatly on the solvent. Therefore it is very important to characterize it for every solvent used for our DNP applications. Our earth field free precession equipment will allow numerous measurements of different f values which are useful for a better interpretation of HB or other effects. REFERENCES 1) Abragam A., The principles of Nuclear Magnetism (Clarendon Press, Oxford 1961). 2) Muller-Warmuth W., Meise Gresch K., Ad. Magn. Res. 1983 (2), 1. 3) Salvi A., Rev. Phys. Ap. 1970 (5), 131. 4) Bene J.G., Phys. Reports 1980 (58), 213. 5) Ayant Y., Kernevez K., Secourgeon, L., Tordo, P., Submitted for Congress Ampere "Weak field Dynamic Nuclear Polarization with Phosphorus radicals". 6) Ayant Y., Besson R. Salvi A., J. Phys. 1975 (36), 571.

202

19F-SPIN-LATTICE RELAXATION OF PFii INTERCALATED IN GRAPHITE I. Stang, M. Kraus, K. Liiders Fachbereich Physik, Freie Universitat Berlin, D-I000 Berlin 33, Fed. Rep. of Germany

ABSTRACT . Second stage graphite intercalation compounds were prepared by intercalation of PF6" and nitromethane into HOPG. The temperature dependence ofthe spin-lattice relaxation rate between 50 - 300 K reveals three maxima, which we attribute to anisotropic rotations and diffusive motion. The angular dependence of T I is measured at different temperatures. PACS numbers: 76.60E, 66.30, 68.65

INTRODUCTION A lot of fluorine containing compounds react with graphite yielding graphite intercalation compounds (GIC) in which the inserted molecules may perform motions limited by the adjacent graphite layers. Since the intercalation is usually accompanied by a redox reaction a number of different molecules may be intercalated simultaneously. In order to avoid this we prepared a GIC containing only one fluorine compound [I]. We obtained a second stage compound intercalated with PF6" and nitromethane as it was proved by NMR [2]. We used highly oriented pyrolytic graphite (HOP G) - a polycrystalline material in which the graphite c-axes are aligned normal to the platelet surface whereas the orientation of crystallites perpendicular to the c-axis is random. This allows angular dependent measurements where 0 is the angle between the graphite c-axis and Bo. RESULTS Temperature dependent measurements of the 19F-spin lattice relaxation rate Til between 50 K and room temperature (v = 52 MHz) show two large maxima at about 80 K (max. I) and 150 K (max. II) and a smaller one at about 280 K (max. III). The slopes above and below the two low temperature maxima are different as it is known for a number of layered compounds (probably due to the disordered arrangement of the intercalated molecules leading to distributions of correlation times or activation energies [3]). At room temperature the angular dependence of Til (Fig. 1) is very well fitted by a (3cos 2 0- 1)2-dependence. If deuterated nitromethane is intercalated the relaxation rate is reduced by a factor of '" 0.35 and the angular dependence is almost removed. Observing the relaxation rate of protons in nitromethane a maximum is found slightly above of that of fluorine. These results indicate that max. III is due to diffusive motion of the protons of nitromethane relative to fluorines of PF6". The angular dependencies of Til slightly above of maxima I and II are totally different from what is observed at room temperature (Fig. 2). There is only a small difference compared to deuterated samples indicating that the main source of relaxation is the intramolecular interaction. The linewidth above", 50 K is partially averaged out, but only above 200 K the isotropic rotation is fast enough to average out the linewidth below the field inhomogeneity. DISCUSSION The angular dependence of Til at room temperature is well described by the theory of Avogadro and Villa [4] which treats planar diffusion: The spectral density contains the function r(w) describing the distance-correlation which diverges if w becomes small (WT