A study of the S(3P2,1,0;1D2) production in the 193 nm photodissociation of CH3S(X)

The dynamics of S(3P2,1,0;1D2) production from the 193 nm photodissociation of CH3SCH3 has been studied using 2+1 resonance-enhanced multiphoton ionization techniques. The 193 nm photodissociation cross section for the formation of S from CH3S initially prepared in the photodissociation of CH3SCH3 is estimated to be 1×10−18 cm2. The branching ratio for S(3P)/S(1D) is found to be 0.15/0.85. The fine-structure distribution observed for product S(3P2,1,0) is nearly statistical. Possible potential energy surfaces involved in the 193 nm photodissociation of CH3S(X̃) have been examined theoretically along the CH3–S dissociation coordinate in C3v symmetry. These calculations suggest that predissociation of CH3S(C̃ 2A2) via the repulsive CH3S(Ẽ 2E) surface is most likely responsible for the efficient production of S(1D). For vibrationally excited CH3S(X̃), a viable mechanism for the dominant production of S(1D) may involve direct dissociation via the CH3S(Ẽ 2E) state formed in the 193 nm photoexcitation.