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 (A) over tilde (2)A(1) <-- (X) over tilde E-2 electronic band (T(0)congruent to 26 400 cm(-1)) and an unstructured band near 45 600 cm(-1). At all energies, only one major channel, CH3((X) over tilde (2)A(2)") + S(P-3(j)), was observed. Photofragment yield spectra for the (A) over tilde (2)A(1) <-- (X) over tilde E-2 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(P-3(j)) fine-structure distribution for each vibrational level of the CH3 product. Photofragment angular distributions were found to be highly anisotropic (beta= - 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 (A) over tilde (2)A(1) State is predissociated. Results at 45 600 cm(-1) imply that dissociation occurs on the repulsive (B) over tilde (2)A(2) state. (C) 1999 American Institute of Physics. [S0021-9606(99)04201-4].