Photodissociation study of CS2 at 193 nm using slice imaging

The photodissociation of CS2 at 193 nm (51 700) cm−1) is studied using the slice imaging technique, and velocity distributions for state selected S(3P2,1,0) and S(1D2) photofragments are measured. From the analysis of the speed distributions we determine the S(3P2,1,0)/S(1D2) branching ratio to be 1.5±0.4. The partially resolved S-atom speed distributions peak at intermediate speeds, indicating substantial rovibrational excitation of the CS sibling fragment. By modeling this CS propensity using a Franck–Condon analysis between the X(1Σg+) and the excited B21 state, we estimate the origin of the excited state to be located at ∼45 600 cm−1. From the S-atom angular distributions, we determine the spatial anisotropy parameter β, and find that the value for S(3P2,1,0) is slightly speed dependent with an average value of ∼0.2. The β values for S(1D2) are strongly speed dependent, reaching the value of 0.6 at intermediate speeds and an average value of 0.2 at low and high speeds. From the observed β values we conclude that the CS2 molecule is highly bent (∼115°) prior to dissociation, while the dissociation lifetime is on the order of a rotational period.