S-2(A(1)DELTA) PRODUCTION IN THE REACTION OF S D-1 ATOMS WITH COS - SPECTROSCOPY AND DYNAMICS

The reaction S(D-1) + COS(X (1)Sigma(+))-->S-2(a (1)Delta) + CO(X (1)S igma(+)) has been studied using pulsed photolytic production of S(D-1) together with laser-induced fluorescence detection of S-2(a (1)Delta) . S(D-1) was produced by 212.8 nm (Nd:YAG fifth harmonic) photolysis o f OCS. The nascent S-2(a (1)Delta) product has been observed under sin gle collision conditions. Rotational and vibrational population distri butions for excited S-2(a (1)Delta) have been obtained. The observed v ibrational distribution was analyzed using surprisal analysis and was found to be much colder than predicted by purely statistical arguments , although it extends to at least upsilon=6. A rotational population d istribution was obtained for upsilon=2 of the S-2(a (1)Delta) state. I t shows a maximum around J=45, which is hotter-than thermal but much c older than the statistical prediction. Resolved emission experiments w ere performed to verify calculated Franck-Condon factors for the S(2)f (1)Delta-a (1)Delta transition. Ab initio calculations suggest severa l possible routes leading from reactants to products in the singlet re action channel but predict significant reaction barriers for the tripl et channel. (C) 1998 American Institute of Physics. [S0021-9606(98)011 44-1].