Depolarization of Photoluminescence of Isotropic Solutions Produced by Excitation Energy Migration

Abstract

A theory of the excitation energy transfer between like molecules in isotropic solution based on a centre or shell model of a primarily excited luminescent molecule and on the extended Förster “excitation master equation” has been elaborated. Fluorescence and phosphorescence depolarization are shown to be governed by singlet-singlet energy migration and described by the same expression. The comparison of the theoretical curve with the experimental data obtained by Gondo et al. (1975) for benzo[f]quinoline in ethanol glass at 77 K results in the following critical distance R0 for the excitation energy migration: 21.5 Å for fluorescence and phosphorescence, respectively.