Abstract

Pyrazine has long been considered to be a molecule with intermediate case level structure. The spontaneous emission from an excited state of such a molecule does not exhibit a simple exponential decay with time. The observed nonexponential decay is interpreted as arising from rapid evolution of the initially formed singlet wavepacket to generate mixed singlet-triplet levels, followed by slow depopulation via radiation from the singlet components of the mixed levels. The evolution of the wavepacket is, in the absence of coupling to the radiation field a coherent process, so the mixed levels generated have well defined phase relations and can generate a beat spectrum.

© 1984 Optical Society of America