Multiple Electron Resonance Spectroscopy

Abragam and Bleaney/H) and others.o6---19) Basically, this volume deals with those spectroscopic techniques that use EPR as a detection method. Chapters 2 through 5 cover the experimental and theoretical aspects of multiple resonance spectroscopy. Chapters 6 through 12 are systems-oriented and deal with the multiple resonance techniques applied to crystals, glasses, bioproteins, polymers, and triplets. The concepts of the first five chapters illustrate the strength of MERS to solve a broad range of problems. Chapters 13 and 14 are rather detailed introductions to two of the latest new applications: TRIPLE resonance and optical perturbations in EPR. The latter is to be distinguished from the OMDR (optical magnetic double resonance) techniques, in which the optical system is the detection method. References 1. E. J. Zavoisky, J. Phys. U.S.S.R. 9, 211 (1945). 2. J. S. Hyde, Ann. Rev. Phys. Chern. 25, 407 (1974). 3. N. M. Atherton, Electron Spin Resonance (Specialist Periodical Reports, The Chemical Society, London) 1, 32 (1972); 2, 35 (1974). 4. J. H. Freed, Ann. Rev. Phys. Chern. 23, 265 (1972). 5. J. E. Wertz and J. R. Bolton, Electron Spin Resonance, Elementary Theory and Practical Applications, p. xii, McGraw-Hill Book Co., New York (1972). 6. G. Feher, Phys. Rev. 103,834 (1956). 7. P. P. Sorokin, G. J. Lasher, and I. L. Gelles, Phys. Rev. 118, 939 (1960). 8. N. Bloembergen, S. Shapiro, P. S. Pershan, and J. O. Artman, Phys. Rev. 114,445 (1959).

1. Multiple Electron Resonance Spectroscopy: An Introduction.- 2. Instrumentation and Experimental Methods in Double Resonance.- 1. endor.- 1.1. The Basic endor Spectrometer.- 1.2. endor Measurements.- 1.3. Experimental Effects in endor Studies.- 2. eldor.- 2.1. General Remarks.- 2.2. Models of eldor Spectrometers.- 2.3. The Varian eldor Cavity.- 2.4. Summary.- References.- 3. Theory of Multiple Resonance and esr Saturation in Liquids and Related Media.- 1. Introduction to Saturation.- 1.1. General Considerations.- 1.2. A Simple Line: Two-Level System.- 1.3. A Simple Line: Multilevel System.- 2. eldor.- 3. endor.- 3.1. General Considerations.- 3.2. Neglect of Coherence Effects.- 3.3. Coherence Effects in endor.- 3.4. Triple Resonance.- 4. Transition Probabilities.- 4.1. eldor—Generalized No Saturation of Observing Mode.- 4.2. endor—Limiting Enhancements.- 4.3. Triple Resonance—Limiting Enhancements.- 4.4. Expressions for the Linewidths and the Transition Probabilities.- 5. Heisenberg Spin Exchange and Chemical Exchange.- 6. General Approach.- 6.1. Diagram Method.- 6.2. Effects of Degenerate States and Transitions.- 7. Average endor and eldor.- 7.1. Average endor.- 7.2. Average eldor.- 8. Saturation and Double Resonance in the Slow-Tumbling Region.- 8.1. General Considerations.- 8.2. Saturation: A Simple Line.- 8.3. eldor: A Simple Line.- Appendix. General Properties of the Transition Probability Matrix W.- References.- 4. Solution endor.- 1. Introduction.- 2. Analysis of endor Frequencies.- 2.1. Transition Frequencies.- 2.2. Assignment of Transitions.- 2.3. Applications of Proton endor.- 2.4. endor of Other Nuclei.- 3. Analysis of endor Intensities and Linewidths.- 3.1. Relaxation and endor.- 3.2. Relaxation Mechanisms.- 3.3. Linewidths.- 4. Conclusion.- References.- 5. Modulation Effects in Multiple Electron Resonance Spectroscopy.- 1. Introduction.- 2. Theory.- 3. Examples of Zeeman Modulation Effects.- 3.1. Modulation Effects in the Resonance and Double Resonance Spectra of Spin Labels.- 3.2. Modulation Effects in the Resonance and Double Resonance Spectra of Solid-State Organic Radicals.- References.- 6. Disordered Matrices.- 1. endor in Disordered Matrices.- 1.1. Anisotropic endor.- 1.2. Matrix endor.- 2. eldor in Disordered Matrices.- 2.1. Powder eldor—Hyperfine Information.- 2.2. Spin Packet Model and Spin Diffusion in Inhomogeneous Lines.- 2.3. Cross-Relaxation Studies.- References.- 7. Crystalline Systems.- 1. Introduction.- 2. Determination of Anisotropic Hyperfine Splitting Tensors.- 2.1. endor.- 2.2. eldor.- 2.3. Second-Order Effects.- 2.4. Signs of Hyperfine Constants.- 3. Unique Role Played by endor.- 3.1. Determination of Small Splittings.- 3.2. Determination of Quadrupole Couplings.- 3.3. Reaction Mechanism of Radical Formation.- 3.4. Distant endor.- 4. Unique Role Played by eldor.- 4.1. Spin Exchange Processes.- 4.2. Determination of Large Splittings.- 4.3. Identification of Radicals with Large Quadrupole Interactions.- 5. Complementary Role Played by endor and eldor.- 5.1. Separation of Overlapping Spectra.- 5.2. Methyl Groups Undergoing Tunneling Rotation.- 5.3. Proton-Deuteron Exchange.- 5.4. Intramolecular Motion.- References.- 8. endor on Hemes and Hemoproteins.- 1. Introduction.- 1.1. Biological Role of Hemoproteins.- 1.2. Paramagnetism of Heme Systems.- 1.3. Rationale for Using endor to Study Heme.- 2. endor Technique Applied to Heme Systems.- 2.1. Factors Affecting the endor Signal.- 2.2. The endor Spectrometer.- 3. endor Measurements on Hemes and Hemoproteins.- 3.1. endor from High-Spin (S = 5/2) Ferric Heme Proteins.- 3.2. endor Studies on High-Spin Ferric Hemin Compounds.- 3.3. endor from Low-Spin (S = ½) Ferric Hemes and Hemoproteins.- 4. Summary.- References.- 9. endor and eldor on Iron-Sulfur Proteins.- 1. Introduction.- 2. Theory.- 2.1. Fundamental Interactions in epr.- 2.2. The Phenomenon of endor.- 2.3. The Phenomenon of eldor.- 3. Instrumentation.- 3.1. endor Instrumentation.- 3.2. eldor Instrumentation.- 4. Iron-Sulfur Proteins—endor and eldor.- 4.1. Two-Iron Ferredoxins.- 4.2. Four-Iron-Sulfur Proteins.- 4.3. Eight-Iron Ferredoxins.- 5. Summary.- References.- 10. Radiation Biophysics.- 1. Introduction.- 2. Indirect Effects.- 3. Nucleic Acid Constituents.- 4. Protein Constituents.- 5. Conclusion.- References.- 11. Polymer Studies.- 1. Introduction.- 2. Irradiated Polymers.- 3. Spin Probes within Polymeric Matrices.- 3.1. Temperature Dependence of Single-Line eldor.- 3.2. Motion of Interstitial Molecules.- 4. Spin-Labeled Polymers.- 5. Concluding Remarks.- References.- 12. endor of Triplet State Systems in Solids.- 1. Introduction.- 2. Nature of Triplet States of Organic Molecules.- 3. Spin Hamiltonian.- 3.1. Form and Determination of Parameters.- 3.2. Physical Properties Deduced from endor.- 3.3. Experimental Approaches.- 4. Examples of Systems Studied.- 4.1. Ground-State Triplets.- 4.2. Excited Triplet States of Organic Molecules.- 4.3. Defects in Solids.- 4.4. Other S = 1 Systems.- 5. Summary.- References.- 13. Principles and Applications of Optical Perturbation-Electron Paramagnetic Resonance (opepr).- 1. Introduction.- 2. Experimental Technique.- 2.1. Single-Light-Pulse (SLP) Experiment.- 2.2. Continuous-Wave (CW) Experiment.- 3. Theoretical Treatment of opepr Experiments.- 3.1. Kinetic Theory of the Transient Triplet epr Spectrum.- 3.2. Expressions for the Transient Triplet epr Signal Intensities in an SLP Experiment.- 3.3. Expressions for the epr Signal Intensities in a CW Experiment.- 3.4. Analysis of the Transient Kinetics in a Harmonic Modulation CW Experiment.- 4. Examples and Applications.- 4.1. Porphyrins.- 4.2. Chlorophylls in Vitro and in Vivo.- 4.3. Triplet-Triplet Absorption.- 4.4. Photoreduction of Porphyrins to Chlorins by Tertiary Amines in the Visible Spectral Range.- 4.5. Determination of Kinetic Rate Constants of Recombination of Radicals in Solutions.- 4.6. Photoionization of Alkali Metals in Solutions in the Presence of Crown Ethers.- 5. Concluding Remarks.- References.- 14. Electron-Nuclear-Nuclear triple Resonance of Radicals in Solutions.- 1. Introduction.- 2. Experimental Aspects.- 2.1. General Considerations.- 2.2. Apparatus.- 2.3. Modulation Schemes for triple Resonance.- 3. Theoretical Aspects.- 3.1. Special triple in the Four-Level Transition Scheme.- 3.2. General triple in the Eight-Level Transition Scheme.- 4. Comparison between Theory and Experiment.- 4.1. Special triple Resonance.- 4.2. General triple Resonance.- 5. Applications of triple-in-Solution.- 5.1. Fluorenon-Alkali Metal Ion Pairs.- 5.2. Diphenylpicrylhydrazyl (DPPH).- 6. Conclusion.- References.