Picosecond fluorescence study of the energy dependence of geminate recombination kinetics in nonpolar liquids

The dynamics of geminate ion-electron recombination following multiple photon 305 nm picosecond laser photoionization have been observed for a series of aromatic solutes in trans-decalin solution by time-resolving the recombination fluorescence. The nonexponential recombination dynamics are the same for the three solutes N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD), 1-aminonaphthalene, and anthracene, despite the differences in electron excess energy. Recombination fluorescence is unresolvably fast for 2,5-diphenyloxazole (PPO). The implication of these results regarding the dependence of the average electron thermalization distance on excess energy is briefly discussed.