Photodissociation Imaging of Diatomic Sulfur (S2)

Abstract

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((3)P(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((3)P(2)) + S((3)P(2)) rather than S((3)P(2)) + S((3)P(1)). The wavelength dependence of data for the S((3)P(2)) + S((3)P(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.