Photodissociation of CS2 at 193 nm investigated by polarised photofragment translational spectroscopy

The predissociation dynamics of CS2 in the <(A)over tilde>(B-1(2)) state have been investigated by means of high resolution photofragment translational spectroscopy at 193 nm. The photofragment translational energy distributions derived from the time-of-night (TOF) distributions of the CS fragment are qualitatively similar to the ones obtained in previous investigations. Detailed measurements carried out with a linearly polarised photolysis laser reveal a pronounced anisotropy of the fragment recoil which is dependent on the translational energy and on the molecular beam carrier gas. It is possible to partition each TOF distribution of the CS fragment into two components corresponding to the formation of S(P-3) and S(D-1) partner fragments, respectively, in a manner consistent with recent branching ratio determinations. In the case of the Ne beam this partitioning leads to the anisotropy parameters beta(S D-1)approximate to 0.2 and beta(S 3P)approximate to 1.0. These results indicate that the overall photodissociation process occurs on a time scale of similar to 1.5 ps and that the formation of CS + S(D-1) proceeds through a strongly bent transition state.