Photodetachment-photoelectron spectroscopy of HS ^-·H ₂S and DS ^-·D ₂S: The transition states of the SH + H ₂S and SD + D ₂S reactions

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 ₂S and SD + D ₂S reactions are investigated by photodetachment-photoelectron spectroscopy of HS ^-·H ₂S and DS ^-·D ₂S. 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.