Photodissociation Imaging of Diatomic Sulfur (S2)

The photodissociation of diatomic sulfur, S-2, in the region of the first dissociation limit is studied with velocity map imaging. Correlated fine structure distributions P(J1,J2) for the two S(P-3(j)) fragments are determined at selected photolysis wavelengths. Image analysis of the speed distributions of the atomic fragments following product-state-specific detection results in a revision of the bond energy to D-0 = 35636.9 +/- 2.5 cm(-1) with respect to the lowest rovibrational level. This value arises from reinterpretation of previous spectroscopic data showing onset of predissociation in the B-3 Sigma u(-) state, as the measurements presented here demonstrate that the long-range correlation of the excited state invoked as causing the dissociation is S(P-3(2)) + S(P-3(2)) rather than S(P-3(2)) + S(P-3(1)). The wavelength dependence of data for the S(P-3(2)) + S(P-3(2)) channel suggests involvement of photoexcitation through the optically forbidden Herzberg continuum bands in addition to dissociation initiated via the optically allowed B-3 Sigma u(-)-X-3 Sigma(-)(g) and B ''(3)Pi u(-)X(3)Sigma(-)(g) bands. Changes in product recoil velocity angular distributions and atomic angular momentum polarization were also measured as a function of dissociation wavelength. The results are compared with predictions from an adiabatic model for dissociation, which provides a basis for interpretation but does not explain quantitatively the experimental results.