Photodissociation dynamics of H2S at 121.6 nm and a determination of the potential energy function of SH(A 2Σ+)

Abstract

A new and improved version of the technique of H atom photofragment translational spectroscopy has been applied to a study of H2S photodissociation at 121.6 nm. The primary fragmentation pathways leading to H+SH(A) fragments and H+H+S(1 D) atoms are observed to dominate the product yield; the yield of H atoms formed in conjunction with ground state SH(X) fragments is undetectably small. The majority of the SH(A) fragments are formed in their v=0 level with a rotational state population distribution that spans all possible bound and quasibound rotational levels. The experimental determination of the energies of these hitherto unobserved high rotational states has enabled a refinement of the SH(A) potential energy function, an improved estimate of the SH(A) well depth (9280±600 cm− 1), and thus of the SH(X) ground state bond dissociation energyD 0 0 (S–H)=3.71±0.07 eV. All aspects of the observed energy disposal in the title photodissociation process may be understood, qualitatively, if it is assumed that (i) the primary fragmentations occur on the B̃ 1 A 1potential energy surface and (ii) Flouquet’s a b i n i t i o calculations of portions of this surface [Chem. Phys. 1 3, 257 (1976)] correctly predict its gross topological features.