ESR Studies of Heisenberg Spin Exchange. III. An ELDOR Study

Abstract

We report the first quantitative test of the theory for electron–electron double resonance (ELDOR) of free radicals in solution. The reduction factors $R$ for the ELDOR spectra of aqueous solutions of the peroxylamine disulfonate dianion radical (PADS) were examined and shown to fit the theory given by Hyde, Chien, and Freed in the extrapolated limit of infinite pump power. Some of the experimental and theoretical problems are discussed. The effect of exchange on the saturation properties of PADS was investigated and shown to agree, within experimental error, with the theory discussed in Part I of this series. The implications of these results for the determination of relaxation times in complex systems are briefly discussed.