Abstract

With heat pulse technique (pulse duration Δt ≧ 20 ns) we measured the effects of phonons on the persistent spectral holes of dye molecules in thin organic films, e.g. Langmuir-Blodgett films, or of dye molecules adsorbed at the surface of crystals. The measurements include phonon memory¹ and real time effects of phonons, i.e., the irreversible and the reversible phonon-induced filling in the center of the spectral hole. In particular we measured the dependence on the duration and on the power density or calculated temperature T_H of the heat pulses. The dependence of the fluorescence intensity I_O of the first vibronic zero phonon line on the number N of the irradiated heat pulses (or to be precise on the time t = N•Δt) in the case of the phonon memory is demonstrated in Fig. 1. The observed logarithmic time dependence is explained by a theory based on thermally activated processes in double well potentials²with constant density of states concerning their barrier heights.

© 1984 Optical Society of America