PREFACE INTRODUCTION TO MAGNET RESONANCE AND EPR What are EPR (or ESR, EMR) and NMR? Why EPR? Why is resonance in the name and should it still be there? EPR compared to other methods with atomic resolution EPR compared to UV, visible and IR spectroscopy Small energy gap between resonant energy levels SURVEY OF EXPERIMENTAL FINDINGS RESULTING FROM THE MANY MODERN EPR TECHNIQUES CONCEPT OF SPIN HAMILTONIAN Electron-Zeeman Interaction Fine-Structure Interaction Hyperfine Interaction Nuclear Zeeman Interaction Nuclear Quadrupole Interaction Resonance Phenomenon EXPERIMENTAL TECHNIQUES (INSTRUMENTATION, RESONATORS, DETECTION, ETC.) Key features of EPR instrumentation DATA ACQUISITION Chart Recorder and phase sensitive detection of field modulation Basic methods using digital recorders controlled by computer Example of acquiring a simple CW-EPR spectrum using a modern EPR LINESHAPES Intrinsic line width (T1 and T2 ) Width of overall spectral envelope Homogeneous vs. heterogeneous Anisotropic effects SPIN DELOCALIZATION AND HYPERFINE INTERACTION ELECTRON-ELECTRON INTERACTIONS Excited Triplet states Radical pairs Anisotropic interactions STATIC SYSTEMS VS. TIME CHANGING SYSTEMS CW EPR vs. time domain EPR PARAMAGNET SYSTEMS EXPLORED WITH STATIC (I.E., NOT TIME DOMAIN) EPR Organic doublet state radicals Organic triplet molecules Long- and short-lived radical pairs Paramagnetic inorganic systems PARAMAGNET SYSTEMS EXPLORED WITH STATIC (I.E., NOT TIME DOMAIN) EPR Boltzmann populations vs. ESP (electron spin polarization) Basic ESP types Radical Pair ESP Triplet Radical Pair ESP SPECIFIC EPR TECHNIQUES Multi-frequency continuous-wave EPR (Multi-)Pulse EPR, FT-EPR etc. ENDOR (pulsed) and related methods ESEEM (3-, 4-Pulse, etc.) HYSCORE ELDOR (pulse, 3- and 4-Pulse) Double-Quantum Coherence for Distance Determination Transient EPR DATA ANALYSIS Spectral simulation of static paramagnetic species for identification Spectral simulation of time varying paramagnetic species, typically including ESP Analysis methods typically developed per specific systems Density matrix formulation using Liouville equation Available software (EasySpin, MolecularSophe, ...) APPLICATIONS OF EPR IN LIFE SCIENCES AND MATERIAL SCIENCES Spin labels in membranes Artificial photosynthesis Bird navigation Electron transfer Nanoparticles FUTURE DEVELOPMENTS APPENDICES Useful constants Mathematical formulas and concepts relevant to EPR Recommended advanced reading
