A detailed study of the predissociation dynamics of the 1B2(1Σ+u) state of CS2

The photodissociation dynamics of the 1B2 state of CS2 have been studied for excitation energies between 46 600 and 50 500 cm−1 (214–198 nm). These experiments used a tunable pulsed uv laser to photodissociate jet-cooled CS2 and the resulting atomic S products were detected by single photon VUV laser-induced fluorescence. These data allow for the measurement of the S(1D2):S(3PJ) product branching ratios as a function of vibrational level in the 1B2 state. Because of the low rotational temperature of the jet cooled CS2, we were able to resolve vibrational bands, and simulate the rotational contours for K=0 and K=1 vibrational bands up to 50 100 cm−1 excitation energy, obtaining homogeneous linewidths for these levels. For vibrational levels close to the zero point, the dissociation dynamics, both lifetimes and product branching ratios, were very different for K=0 and K=1 levels at the same energy. In particular, K=1 levels have shorter lifetimes, and a substantially higher yield of S(1D2) product. We propose a model for the dissociation dynamics of the 1B2 state of CS2, based on our results and preliminary ab initio calculations of the potential energy curves for excited states of CS2.