Excimer fluorescence - XI. Solvent-solute energy transfer

Abstract

The rate parameters of solvent-solute energy transfer and of oxygen-solvent quenching have been determined for solutions of 2, 5-diphenyloxazole in benzene, toluene, p -xylene and mesitylene. The role of excited molecules and excimers in transfer to the solute molecules is considered in terms of the Voltz relations, which include the Förster critical transfer distance, the molecular diffusion coefficients, and the solvent excitation migration coefficient. It is proposed that the migration is due to excimer formation and dissociation, and that the energy transfer occurs by a diffusion/migration-controlled collisional process. Dilution of the solvent decreases the migration, but increases the transfer distance, so that the transfer efficiency remains practically constant. The excimer formation and dissociation rate parameters in the pure alkyl benzenes are evaluated.