Photodetachment-photoelectron spectroscopy of HS−·H2S and DS−·D2S: the transition states of the SH + H2S and SD + D2S reactionsElectronic supplementary information (ESI) available: The energies and corresponding geometry parameters of the fully optimized and the constraint anionic structure calculated with Molpro at the RCCSD(T)/aug-cc-pVTZ level. See DOI: 10.1039/b925941d

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 + H 2 S and SD + D 2 S reactions are investigated by photodetachment-photoelectron spectroscopy of HS − ·H 2 S and DS − ·D 2 S. 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. The shuttling motion of the intermediate hydrogen atom in the hydrogen transfer transition state of HS·H 2 S dominates the photodetachment photoelectron spectrum of HS·H 2 S − .