Transition state dynamics of the OH+OH→O+H2O reaction studied by dissociative photodetachment of H2O2−

Abstract

Photoelectron-photofragment coincidence (PPC) spectroscopy has been used to study the dissociative photodetachment of H2O2− and D2O2−. The observed partitioning of photoelectron and photofragment translational energies provides information on the dynamics in the transition state region of the reaction between two hydroxyl radicals: OH+OH→O(3P)+H2O. The data reveal vibrationally resolved product translational energy distributions for both the entrance channel OH+OH and the exit channel O(3P)+H2O upon photodetachment. The total translational energy distribution shows a convoluted vibrational progression consistent with antisymmetric stretch excitation of H2O in the exit channel and OH stretch in the entrance channel. The photoelectron spectra are compared to two-dimensional time-dependent wave packet dynamics simulations based on an anharmonic potential in the anion and a model collinear potential energy surface for the neutral complex. The PPC spectra also yield the dissociation energies D0(H2O2−→H2O+O−)=1.15±0.08 eV and D0(D2O2−→D2O+O−)=1.05±0.08 eV.