Journal of Chemical Physics, Vol.115, No.21, 9727-9732, 2001
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(P-3(2,1,0)) and S(D-1(2)) photofragments are measured. From the analysis of the speed distributions we determine the S(P-3(2,1,0))/S(D-1(2)) 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((1)Sigma (+)(g)) and the excited B-1(2) state, we estimate the origin of the excited state to be located at similar to 45 600 cm(-1). From the S-atom angular distributions, we determine the spatial anisotropy parameter beta, and find that the value for S(P-3(2,1,0)) is slightly speed dependent with an average value of similar to0.2. The beta values for S(D-1(2)) 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 beta values we conclude that the CS2 molecule is highly bent (similar to 115 degrees) prior to dissociation, while the dissociation lifetime is on the order of a rotational period.