Collisional quenching of fluorescence from S2(B 3Σ−u)

Lifetimes of the B 3Σ−u state of S2 in the presence of various quenching gases have been determined from fluorescence decay measurements made with the single-photon time correlation technique. Fluorescence was excited with a pulsed light source of wavelength 292 nm, and observed at 370 nm. He, Ar, Xe, N2, S2, CF4, and C2F6 have been used as quenching gases. At high pressures (?100 torr), a single lifetime of ∼110 nsec is observed, whereas at lower pressures there is a second component with a lifetime of ∼5–30 nsec. From these lifetimes, bimolecular rate constants and thermally averaged cross sections for collisional quenching have been determined. The results are discussed in terms of a model in which two excited states of S2 are either coupled with each other or with the ground state.