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(1D) 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 energy D00 (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 1A1 potential energy surface and (ii) Flouquet’s ab initio calculations of portions of this surface [Chem. Phys. 13, 257 (1976)] correctly predict its gross topological features.