Competing dissociation between the S-Cl and S-S bonds in the photolysis ofS2Cl2 at 248 and 193 nm

The photodissociation of S2Cl2 at 248 and 193 nm has been studied by transl ational spectroscopy. Upon excitation at 248 nm, S2Cl2 undergoes predominan tly the dissociation channels to form the products, (1) S2Cl+Cl and (2) SCl +SCl. The relative yield of (1)/(2) was determined at similar to 3.0:1.0. T he S2Cl+Cl products were detected with two separate product translational e nergy distributions of [E-t] = 14 and 41 kcal/ mol. The slow S2Cl fragment, which is internally excited, undergoes a secondary dissociation to form S- 2+Cl. Dissociation mechanisms which are consistent with the isotropic recoi ling are proposed: the slow component could arise from the ground electroni c state while the fast component would more likely originate from a mixed e xcitation of (1)A and B-1 states (C-2 symmetry). The SCl product with aniso tropy parameter beta = 1.6, on the other hand, should proceed by an excited B-1 state. At 193 nm, a three-body formation of S-2 + 2Cl becomes the more efficient process than the simple S-Cl or S-S bond fission. Assuming that the rupture of both S-Cl bonds occurs in a single kinetic step, a P(E-t) di stribution with [E-t] = 30 kcal/mol is determined. Because of the measured beta = -0.3 for the formation of triple products, a higher B-1 state will b e involved in the excitation. (C) 1999 American Institute of Physics.