Electron spin polarization (CIDEP) studies of the dynamics of geminate free radical reactions

The variation with viscosity of the fraction of radicals which survive re-encounter within the geminate period of a radical recombination reaction is measured using the relative contributions of the triplet and radical pair mechanisms to the electron spin polarization observed in their electron spin resonance spectra. This fraction differs from the fraction of re-encounters as a result of reaction. From a triplet precursor 2% of the radicals produced in a photolysis flash recombine in the geminate cage in methanol but 15% do in propan-1,2-diol.