Pulse radiolysis studies on the formation of singlet excited states of coumarin 153 in cyclohexane solutions

By using the technique of nanosecond pulse radiolysis, pulsed electron beam induced light emission from coumarin dyes in hydrocarbon solvents has been studied. The emission spectra so obtained were similar to the optically excited fluorescence spectra. The emission lifetimes were of the same order as the fluorescence lifetimes in the respective solvents, showing that the emitting species are the same in both the cases viz. singlet excited states of the dyes. In one system viz. C 153 in cyclohexane experiments were carried out in presence of electron and hole scavengers and also the concentration dependence of emission intensity studied over a wide range. From these it is concluded that the solute excited states are formed mainly by energy transfer from the solvent excited states, part of which may arise from excitation by cerenkov light generated in the medium. (author)