On the phosphorescence rise and decay processes of phenanthrene in EPA at 77°K

Abstract

Phosphorescence rise and decay behaviors of phenanthrene have been studied in EPA at 77°K. The rise curves follow exactly an exponential law, and the rate constants obtained from the curves are always larger than or equal to the phosphorescence decay constant, depending on excitation intensity and wavelength. Fluorescence rise curves have been also studied in the same system and found to be time-dependent at t > 0.2 sec after the excitation onset. The results obtained are interpreted in terms of a kinetic model involving a process of the depletion of ground-state molecules caused by excitation to their higher electronic levels, with subsequent population in the lowest excited singlet and triplet states.