In the twenty-five years since its discovery by Zavoiskii, the technique of electron spin resonance (ESR) spectroscopy has provided detailed struc- tural information on a variety of paramagnetic organic and inorganic sys- tems. It is doubtful that even much later than 1945 any chemist would have been so bold as to predict the great diversity of systems which have proved amenable to study by ESR spectroscopy. In this book we have attempted to provide numerous examples of actual ESR spectra to illus- trate the wide scope of application. No attempt has been made to present a comprehensive...