The reaction S(D-1) + COS(X (1)Sigma(+))-->S-2(a (1)Delta) + CO(X (1)Sigma(+)) 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 of OCS. The nascent S-2(a (1)Delta) product has been observed under single collision conditions. Rotational and vibrational population distributions for excited S-2(a (1)Delta) have been obtained. The observed vibrational 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 distribution was obtained for upsilon=2 of the S-2(a (1)Delta) state. It shows a maximum around J=45, which is hotter-than thermal but much colder than the statistical prediction. Resolved emission experiments were performed to verify calculated Franck-Condon factors for the S(2)f (1)Delta-a (1)Delta transition. Ab initio calculations suggest several possible routes leading from reactants to products in the singlet reaction channel but predict significant reaction barriers for the triplet channel.