ELECTRON PARAMAGNETIC RESONANCE - Willkommen

1 R , ELECTRON PARAMAGNETIC RESONANCE uion Elementary Theory and first .g to iidst Practical Applications~ the and 20th :heir Second Edition iere, leas. ney, JOHN A. WElL eeds Department of Chemistry, University of Saskatchewan, Saskatoon, way Saskatchewan, S7N OWO Canada -dge JAMES R. BOLTON Bolton Photosciences Inc., 628 Cheriton Cres. NW, Edmonton, AS T6R 2M5, CanadaI the ILEY BICIENTIENNIALARD ". i1807~ ~ffiWILEY ~ ~: 2 007 ~ _; I> r BICENTIlNNIAL WILEY-INTERSCIENCE A JOHN WILEY & SONS, INC., PUBLICATION r CONTENTS PREFACE xix ACKNOWLEDGMENTS xxiii 1 BASIC PRINCIPLES OF PARAMAGNETIC RESONANCE 1 Introduction / I Historical Perspective / 3 A Simple EPR Spectrometer / 4 Scope of the EPR Technique / 7 Energy Flow in PARAMAGNETIC Systems / II Quantization of Angular Momenta / 13 Relation Between Magnetic Moments and Angular Momenta / 14 Magnetic Field Quantities and Units / 15 Bulk Magnetic Properties / 18 Magnetic Energies and States / 20 Interaction of Magnetic Dipoles with Electromagnetic Radiation / 21 Characteristics of the Spin Systems / 23 The g Factor / 23 Characteristics of Dipolar Interactions / 27 Parallel-Field EPR / 28

2 Vii viii CONTENTS Time-Resolved EPR / 29 References / 79 S Computerology / 29 Notes / 79 EPR Imaging / 30 Further Reading / 80 References / 30 Problems / 80 Notes / 32 Further Reading / 34 4 ZEEMAN ENERGY I Problems / 3S Introduction / 8 2 MAGNETIC INTERACTION BETWEEN PARTICLES 36 Systems with Hil Systems with Rh Introduction / 36 Construction of t Theoretical Considerations of the Hyperfine Interaction / 38 Symmetry-Relate Angular-Momentum and Energy Operators / 40 EPR Line Intensi Spin Operators and Hamiltonians / 41 Statistically Ranr Electronic and Nuclear Zeeman Interactions / 43 Spin-Orbit Coup] Spin Hamiltonian Including Isotropic Modeling of g / Hyperfine Interaction / 46 Comparative OVI Energy Levels of a System with One Unpaired ELECTRON and One Nucleus with I=!

3 / 47 Energy Levels of a System with S = ! and I = I / 50 References / 111 Notes / 112 Further Reading / 11 Signs of Isotropic Hyperfine Coupling Constants / 53 Problems / 114 Dipolar Interactions Between Electrons / 54 References / 54 5 HYPERFINE (A) ANI Notes / 55 Introduction / I Further Reading / 56 Origin of the Ani Problems / 56 Hyperfine Interac 3 ISOTROPIC HYPERFINE EFFECTS IN EPR SPECTRA 58 Determination an Hyperfine Matrix Introduction / 58 The Anise Hyperfine Splitting from Protons / 59 The Case Single Set of Equivalent Protons / S9 I Multiple Sets of Equivalent Protons / 62 ' Hyperfine Splittings from Other Nuclei with I=!

4 / 68 Hyperfine Splittings from Nuclei with I > ! / 69 ' Combined g and Useful Rules for the Interpretation of EPR Spectra / 74 Multiple Hyperfii Higher-Order Contributions to Hyperfine Splittings / 75 Systems With I : Deviations from the Simple Multinomial Scheme / 77 Hyperfine Powde Other Problems Encountered in EPR Spectra of References / 150 Free Radicals / 77 Notes / 151 Some Interesting 7T-Type Free Radicals / 78 Further Reading / 15 CONTENTS ix References / 79 Notes / 79 Further Reading / 80 Problems / 80 4 ZEEMAN ENERGY (g) ANISOTROPY 85 Introduction / 85 Systems with High Local Symmetry / 88 36 Systems with Rhombic Local Symmetry / 90 Construction of the g Matrix / 92 Symmetry-Related Sites / 96 EPR Line Intensities / 97 Statistically Randomly Oriented Solids / 99 Spin-Orbit Coupling and Quantum-Mechanical Modeling of g / 105 Comparative Overview / 110 References / I II Notes / 112 Further Reading / 114 Problems / 114 5 HYPERFINE (A)

5 ANISOTROPY 118 Introduction / 118 Origin of the Anisotropic Part of the Hyperfine Interaction / 120 Determination and Interpretation of the Hyperfine Matrix / 122 58 The Anisotropic Breit-Rabi Case / 122 The Case of Dominant ELECTRON Zeeman Energy / J24 General Case / 126 The Case of B ~ Bhf / 128 The Case of B ; / 141 Combined g and Hyperfine Anisotropy / 143 Multiple Hyperfine Matrices / 144 Systems With I > ~ / 144 Hyperfine Powder Lineshapes / 145 References / 150 Notes / 151 Further Reading / 152 X CONTENTS Problems / 152 References / 221 Notes / 222 6 SYSTEMS WITH MORE THAN ONE UNPAIRED ELECTRON 158 Further Reading / 22: Introduction / 158 Problems / 223 Spin Hamiltonian for Two Interacting Electrons / ELECTRON -Exchange Interaction / 160 159 8 TRANSITION-GROU ELECTRON - ELECTRON Dipole Interaction / 162 Introduction / 2: Systems with S = I (Triplet States) / 164 The Electronic G Spin Energies and Eigenfunctions / 165 Species / 227.

6 = 2' Transitions / 172 The EPR Parame Randomly Oriented Triplet Systems / 173 Photo-excited Triplet-State Entities / 177 Thermally Accessible Triplet Entities / 182 Ground-State Triplet Entities / 185 Carbenes and Nitrenes / 185 Dianions of Symmetric Aromatic Hydrocarbons / 187 Tanabe-Sugano [ Crossings / 240 Covalency Effect A Ferroelectric S Some j- ELECTRON : References / 246 Notes / 248 Inorganic Triplet Species / 188 Further Reading / 241 Interacting Radical Pairs / 189 Problems / 249 Biradicals / 190 9 THE INTERPRETAT Systems with S > I / 195 High-Spin and High-Field Energy Terms / 196 Introduction / 2 The Spin Hamiltonian: A Summing up / 197 rr-Type Organic.]

7 Modeling the Spin-Hamiltonian Parameters / References / 200 Notes / 203 Further Reading / 204 Problems / 205 199 Anions ar and Some Anions ar g Factors Origin of Sign of th 7 PARAMAGNETIC SPECIES IN THE GAS PHASE 208 Methyl PI Introduction / 208 Monatomic Gas-Phase Species / 209 and Hype Hyperfine than Prou Diatomic Gas-Phase Species / 211 One-Dim Triatomic and Polyatomic Gas-Phase Molecules / 217 a-Type Organic Laser ELECTRON PARAMAGNETIC RESONANCE / 219 Triplet States ani Other Techniques / 219 Inorganic Radica Reaction Kinetics / 220 Electrically Cone Astro-EPR / 220 Metals / Ixii CONTENTS Metals Dissolved in Ammonia and 10. Amine Solutions / 282 10.

8 Semiconductors / 283 Lir Graphitic Compounds / 285 Co Techniques for Structural Estimates from EPR Data / 285 10. The Newman Superposition Model / 285 10. The Pseudo-cube Method / 286 Me Distances from Parameter D / 286 10, Eatons' Interspin-Distance Formula / 287 10, Summary / 287 Ge References / 287 Longitudin: Notes / 291 Saturation-' Further Reading / 291 Time Depe! Problems / 292 Cc Appendix 9A Huckel Molecular-Orbital Calculations / 294 Ch HMO References / 298 Po HMO Problems / 299 Dynamic N Bio-Oxygei 10 RELAXATION TIMES, L1 NEWIDTHS AND SPIN KINETIC Summary PHENOMENA 301 References / 348 Introduction / 30 I Notes / 351 Spin Relaxation: General Aspects / 302 Further Reading / Spin Temperature and Boltzmann Distribution / 302 Problems / 353 Spin Dynamics / 303 Mechanisms for T I / 305 11 NONCONTINUOI Spin Relaxation.

9 Bloch Model / 308 Magnetization in a Static Magnetic Field / 309 Addition of an Oscillating Magnetic Field / 310 Rotating Frame / 311 Steady-State Solutions of Bloch Equations / 312 Linewidths / 316 Homogeneous Broadening / 316 Inhomogeneous Broadening / 316 Dynamic Lineshape Effects / 317 Generalized Bloch Equations / 318 I Introduction The Idealize The Single] Fourier-Trar Multiple Pul ELECTRON Spi Advanced T Spin Cohere References / 378 Other Theoretical Models / 322 Examples of Line-Broadening Mechanisms / ELECTRON -Spin Exchange / 323 322 Notes / 380 Further Reading I Problems / 382 ELECTRON Transfer / 324 12 r CONTENTS xiii Proton Transfer / 326 Fluxional Motion / 326 Linewidth Variation.

10 Dynamic Hyperfine Contributions / 327 Single Nucleus / 328 Multiple Nuclei / 329 Molecular Tumbling Effects / 333 Dipolar Effects / 335 Spin-Rotation Interaction / 339 General Example / 340 Longitudinal Detection / 342 Saturation-Transfer EPR / 343 Time Dependence of the EPR Signal Amplitude / 343 Concentration Changes / 343 Chemically Induced Dynamic ELECTRON Polarization / 345 Dynamic Nuclear Polarization / 347 Bio-Oxygen / 347 Summary / 347 301 References / 348 Notes / 351 Further Reading / 352 / 302 Problems / 353 11 NONCONTINUOUS EXCITATION OF SPINS 357 Introduction / 357 The Idealized B, Switch-on / 359o The Single B, Pulse / 362 Fourier-Transform EPR and FID Analysis / 364 Multiple Pulses / 368 ELECTRON Spin-Echo Envelope Modulation / 369 Advanced Techniques / 375 Spin Coherence and Correlation / 375 References / 378 Notes / 380 Further Reading / 381 Problems / 382.