Vibronic analysis of the <i>A</i> 2<i>A</i>1–<i>X</i> 2<i>E</i> laser-induced fluorescence of jet-cooled CH3S

Abstract

The methylthio (CH3S) radical has been formed by KrF laser photolysis of dimethyl disulfide (CH3SSCH3) in a free-jet expansion. The à 2A1←X̃ 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 X̃ (2E3/2 and 2E1/2)was determined to be −259.1 cm−1. Several progressions indicated that ν′2=1098±2,ν3=401±2 cm−1, and (with less certainty) ν′6=635±10 cm−1. The predissociation threshold was estimated to be slightly above 28 016 cm−1, ∼1490 cm−1 above the v′=0 level of the à state. The dispersed fluorescence was observed in the 363–530 nm region. The main progressions give ν■2=1313±5 cm−1, ν″3=727±3 cm−1, and ν■5=1496±6 cm−1. Weaker lines are also consistent with some possible vibrational frequencies ν″1=2776 cm−1, ν■4=2706 cm−1, and ν″6=586 cm−1.