B 3Σu− predissociation and relaxation processes in matrix isolated S2

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Abstract
Spectroscopy of S2 is rare gas solids in re‐examined. Excitation of the B 3Σu− state populates by predissociation–recombination sequence several excited electronic states, which can then be characterized by their fluorescence spectra. The observed spectra are quite analogous to those observed in ’’thermoluminescence’’ experiments. Analysis of the emission and laser excitation spectra yields the spectroscopic constants of several electronic states of S2 in solid Ne. In particular, the data provide direct evidence that the lowest a 1Δg state is located in this matrix 4395 cm−1 above the ground state. Vibrational relaxation within the B 3Σu− state was examined. It exhibits a very steep rate dependence on temperature and enhanced relaxation efficiency with decreasing mass of the host atoms. It is proposed that relaxation in S2 is due to a direct multiphonon process, and that unlike relaxation in light hydride molecules, the molecular rotation is unimportant.