Photodetachment–photoelectron spectroscopy of HS−·H2S and DS−·D2S: the transition states of the SH + H2S and SD + D2S reactions

Abstract

The transition state region for neutral hydrogen transfer reactions can be accessed by photodetachment of a stable negative ion with a geometry similar to that of the neutral transition state. In this work the SH + H₂S and SD + D₂S reactions are investigated by photodetachment–photoelectron spectroscopy of HS⁻·H₂S and DS⁻·D₂S. The spectra exhibit vibrational structure which is attributed to the antisymmetric stretching mode (H-atom motion) of the neutral transitions state for H-atom transfer. The spectra are compared to one-dimensional simulations performed using a wave packet propagation scheme. Electronic structure calculations of the anionic, neutral and transition-state geometries and calculations of the vertical detachment energy at different levels of theory are used to support the analysis of the spectra. A vertical detachment energy VDE of 3.06 eV has been determined.