Photodissociation spectroscopy and dynamics of the methylthio radical (CH3S)

The photodissociation spectroscopy and dynamics of the CH3S and CD3S radicals have been investigated using fast radical beam photofragment spectroscopy of the à 2A1←X̃ 2E electronic band (T0≅26 400 cm−1) and an unstructured band near 45 600 cm−1. At all energies, only one major channel, CH3(X̃ 2A2″)+S(3Pj), was observed. Photofragment yield spectra for the à 2A1←X̃ 2E electronic band show resolved vibrational progressions extending well beyond those seen in laser-induced fluorescence studies of this band. Photofragment translational energy distributions yield the S(3Pj) fine-structure distribution for each vibrational level of the CH3 product. Photofragment angular distributions were found to be highly anisotropic (β=−0.2 to −1.0±0.1) with increasing anisotropy at higher photon energies. The results yield a refined heat of formation for CH3S (1.346±0.018 eV) as well as the mechanism by which the à 2A1 state is predissociated. Results at 45 600 cm−1 imply that dissociation occurs on the repulsive B̃ 2A2 state.