Fundamentals of Spin Exchange

This book is a comprehensive summary of 50 years of research from theoretical predictions to experimental confirmation of the manifestation of spin exchange in EPR spectroscopy.

The author unfolds the details of comprehensive state of the art of theoretical calculations, which have been proven to become the core of the paradigm shift in spin exchange and set the direction for the future of spin exchange research.

The book refers to important experimental data that confirms the theory. It describes the modern protocol for determining the bi-molecular spin exchange rate from the EPR spectra, which will be especially interesting for experimentalists.

Given its scope, the book will benefit all researchers engaged in theory and experiments in the area of spin exchange and its manifestations in EPR spectroscopy, where many remarkable applications of the spin probe have been developed.

Auteur

Internationally recognized specialist in chemical physics, Kev M. Salikhov is an active participant of international spin chemistry and magnetic radio spectroscopy communities. For the past 50 years Prof. K.M. Salikhov has made an outstanding contribution to the theoretical foundations of spin chemistry, the theory of bi-molecular spin exchange and the theory of the pulse EPR spectroscopy. K.M. Salikhov's theoretical predictions were practically all confirmed in experiments and opened the opportunities for development of many experimental techniques and led to innovation of research methodologies throughout the world. Books on these fields of modern science which he wrote in collaboration with other scientists became textbooks for many specialists all over the world.

Résumé
Spin exchange between paramagnetic particles is one of the few elementary bimolecular processes in solutions that is readily accessible to detailed experimental studies and to strict theoretical description. Due to this fact spin exchange is now widely used in solving various problems of chemistry, physics, and molecular biology. Spin exchange allows one to study in detail elementary acts of collisions of molecules. By use of spin exchange one can obtain quantitative information on collision rates of molecules in solutions, steric hinderance in collisions, electrostatic interactions in collisions of charged particles, and overlap of electron orbitals in collisions. Par­ ticularly valuable is the possibility of using spin exchange to study col­ lisions in such complex systems as polymer solutions, multicomponent mix­ tures, heterogeneous mixtures, and especially biological systems. This monograph contains a comprehensive description of spin exchange in solutions. It consists of four chapters. The introductory chapter contains a brief summary of the physical principles of spin exchange and outlines the range of its main applications. In this chapter a historic background of research in this field is also given. The second chapter contains a com­ prehensive presentation of the theory of spin exchange including that of its spectroscopic manifestations. The third chapter is devoted to a detailed description of the technique of experimental studies of spin exchange. The last - the fourth - chapter summarizes the results of experimental studies of spin exchange and considers various applications of spin exchange in che­ mistry, molecular physics, and biology.

Contenu
Preface.- Introduction.- Bimolecular spin exchange process.- Exchange interaction of two paramagnetic particles.- The nature of exchange interaction.- Spin Hamiltonian of the exchange interaction.- Exchange integral.- Exchange interaction of multielectronic systems. Electron delocalization and spin polarization.- Semiempirical estimates of the exchange integral.- Exchange integral in density functional theory.- Spin density matrix. Quantum spin coherence.- Elementary act of spin exchange. Spin dynamics of a pair of paramagnetic particles.- Equivalent and non-equivalent spin exchange.- Dipole-dipole spin-spin interaction.- Spin Hamiltonian of the dipole-dipole interaction of paramagnetic particles. -Spin dynamics of a pair of paramagnetic particles.- Comparison of spin dynamics in a pair of paramagnetic particles caused by exchange and dipole-dipole interactions.- Modified Bloch kinetic equations for the magnetic moment of a system of paramagnetic particles with allowance for spin exchange.- Spectroscopy of electron paramagnetic resonance as a method of choice for studying spin exchange.- Briefly about the use of spin exchange as a model bimolecular process.- A short history of the development of the theory of spin exchange.- References.- Theoretical calculations of the spin exchange rate constants.- Phenomenological theory.- Overview of Early Theories.- Approximation of sudden switching on and off of the exchange interaction in a collision.- Diffuse passage of the exchange interaction region.- Kinetic equations for the spin matrices of paramagnetic particles taking into account their bimolecular collisions.- Spin exchange between free radicals.- Spin exchange for solutions containing two types of paramagnetic particles with arbitrary electron spins.- Spin exchange between charged paramagnetic particles with electron spins S = 1/2 in electrolytes.- Kinetic equations for the spin density matrices, taking into account the spin dynamics caused by the dipole-dipole interaction, in non-viscous solutions.- References.- Manifestation of spin exchange and dipole-dipole interaction in electron paramagnetic resonance spectroscopy for dilute solution of paramagnetic particles.- General solution for the shape of the spectrum in the linear response case.- A new look at the role of the transfer of spin coherence. Collective modes of evolution of the spin coherence in the system.- Collective modes of motion of the spin coherence for model systems with two and three resonant frequencies.- Analysis of the EPR spectrum of nitroxyl radicals.- How can the equivalent spin exchange rate be extracted from the EPR spectra?.- General observations.- Method for determining the rate constant of equivalent spin exchange from the analysis of EPR spectra.- Effect of saturation of EPR spectra.- General solution for the shape of the spectrum under saturation conditions.- Analysis of the saturation effect for a model system with two resonant frequencies.- Analysis of the saturation effect for a model system with a Gaussian distribution of resonant frequencies.- Analysis of the saturation effect in the EPR spectrum of nitroxyl radicals.- Method for determining the rate of spin-lattice relaxation from the analysis of the effect of saturation of the EPR spectra.- Outlook (perspectives of application of the spin exchange for studying complex systems, spin probes, etc.).- Index.