Laser induced fluorescence of CH3S and CD3S radicals

• DOI: 10.1063/1.447685
• Publication Date: 2003-02-28T17:34:05Z
• Authors: Makoto Suzuki; Gen Inoue; Hajime Akimoto
• Keywords: 0103 physical sciences; 01 natural sciences; 7. Clean energy

Laser-induced fluorescence of the CH3S andCD3S Ã 2A1−X̃ 2E transitions was studied. The 000 bandhead of the 2A1–2E3/2 transition lies at 26 531 cm−1 (376.82 nm) for CH3S and 26 574 cm−1 (376.20 nm) for CD3S. Prominent progressions of the C–S stretching mode (ν3) both in the excitation and dispersed fluorescence spectra are characterized by a doublet structure corresponding to a spin-orbit splitting in the ground state. The band shapes of the transitions 2A1–2E1/2 and 2A1–3E3/2 were found to be quite different from each other, which was interpreted as the difference in the geometry of the spin-orbit sublevels. From the doublet spacings, a spin-orbit coupling constant (A) was obtained; −280±20 cm−1 in CH3S and −260±20 cm−1 in CD3S, in a good agreement with the previous results of laser electron photodetachment studies. The CH3 umbrella mode vibration (ν2) is also active in the vibronic transition. Fundamental vibrational frequencies determined were 1316±4 (ν″2), 740±4 (ν″3), and 403±1 cm−1 (ν′3) for CH3S, and 837±1 (ν2), 667±1 (ν″3) and 395±1 cm−1 (ν3) for CD3S. Fluorescence lifetimes of single vibronic levels were measured to give 0.31 μs for the 000 band of CH3S. Predissociation occurs at v′3=2 and 3 for CH3S and CD3S, respectively.