VIBRONIC ANALYSIS OF THE A2A1-X2E LASER-INDUCED FLUORESCENCE OF JET-COOLED CH3S

The methylthio (CH3S) radical has been formed by KrF laser photolysis of dimethyl disulfide (CH3SSCH3) in a free-jet expansion. The approximately A 2A1 <-- approximately X 2E laser-induced fluorescence excitation spectrum was obtained in the wavelength region 350-382 nm. The origin lies at 26 526.3 cm-1 and the spin-orbital splitting for approximately X (2E3/2 and 2E1/2) was determined to be - 259.1 cm-1. Several progressions indicated that nu-2' = 1098 +/- 2,nu-3' = 401 +/- 2 cm-1, and (with less certainty) nu-6' = 635 +/- 10 cm-1. The predissociation threshold was estimated to be slightly above 28 016 cm-1, approximately 1490 cm-1 above the upsilon' = 0 level of the approximately A state. The dispersed fluorescence was observed in the 363-530 nm region. The main progressions give nu-2" = 1313 +/- 5 cm-1, nu-3" = 727 +/- 3 cm-1, and nu-5" = 1496 +/- 6 cm-1. Weaker lines are also consistent with some possible vibrational frequencies nu-1" = 2776 cm-1, nu-4" = 2706 cm-1, and nu-6" = 586 cm-1.