EXPERIMENTAL AND THEORETICAL-STUDIES OF ISOMERIC CH3S2 AND CH3S2(+)

By combining molecular beam photodissociation and photoionization meas urements with ab initio Gaussian-2 (G2) calculations on the CH3S2 and CH3S2+ systems, we have shown that CH3SS is the dominant isomer formed in the photodissociation process, CH3SSCH3+hv(193 nm) -->CH3S2+CH3. T he experimental ionization energy for CH3SS (8.97+/-0.02 eV) and the h eat of formation at 0 K for CH3SS+ (217.7+/-1.2 kcal/mol) are in excel lent agreement with the G2 results. The photoionization efficiency spe ctrum observed for CH3SS is also consistent with the theoretical predi ction that the Franck-Condon factor for the photoionization process, C H3SS+hv -->CH3SS+ +e-, is not favorable. Based on the statistical mode ling of experimental rates obtained previously for HS loss in the unim olecular decomposition of CH3SSCH3+ and the comparison with G2 ab init io predictions, we conclude that CH2SSH+ is most likely the isomer str ucture formed near the experimental appearance energy (11.07 eV) obser ved for the photodissociative ionization process, CH3SSCH3+hv-->CH3S2CH3+e-.