Electron spin-lattice relaxation in organic free radicals in solutions

Abstract

The electron spin-lattice relaxation times of several semiquinones have been measured as a function of free radical concentration, temperature, solvent, and viscosity, using the pulsed saturation recovery technique. It is found that the recovery of the signal can be fitted to an exponential in all cases within the limits of experimental error. It is also found that the relaxation time T1 is independent of the hyperfine component for a given free radical. Three different models for the liquid state have been employed to analyze the data and it has been postulated that the data, both in liquids and frozen liquids can be explained on the basis of a hindered motion, in hydrogen bonding solvents. A brief review of the earlier theoretical and experimental studies on electron spin-lattice relaxation of free radicals in solutions is also presented. © 1972, Walter de Gruyter. All rights reserved.