ESR of Reacting Radicals

Abstract

This paper represents a review of my research that was presented upon receiving the 2012 Zavoisky Award given by the Zavoisky Physical-Technical Institute in Kazan, Tatarstan, Russia. It is my belief that my early experiences gave an important background for experimental research and success in the area of ESR (electron spin resonance). I will describe some of these. In addition, I will give some of my educational experience that displayed how random chance was also important as to what research area I adopted. Much of my research has been with ESR of radicals produced by ionizing radiation and some of the more important observations are described. Among them is the initial discovery of chemically induced dynamic electron polarization (CIDEP). Also mentioned are a treatment of second-order hyperfine splittings and a number of issues regarding radical structure. This work also contributed to spectrometer design for time-resolved experiments. Modified Bloch equations were developed to describe the ESR time dependence. A number of observations on the hydrated electron, e aq − , are described, including the finding of an “inverse” CIDEP when e aq − is present with certain counter radicals. Several more recent studies finally explained this behavior. Two topics not used in the presentation are also included: a determination of the relaxation time of e aq − and a determination of relative radical yields in pulse radiolysis. Finally, two other applications of microwave absorption are described, including a new method for determining the dipole moments of photo-excited molecules.