Group theoretical analysis of the [formula omitted] reaction

Abstract

The H3++H2→H2+H3+ proton transfer reaction is complicated due to the proton scrambling from the large amplitude motions in the H5+ intermediate. In order to understand this reaction, high-resolution spectroscopic studies are necessary for the reactants/products and the intermediate, and the group theoretical analysis is an essential aspect in the prediction and interpretation of these spectra. With five indistinguishable protons, H5+ is characterized using the G240 complete nuclear permutation-inversion (CNPI) group. For most of the configurations sampled by the reaction path, the feasible permutations depend on the distance between the H3+ and H2 fragments. Subgroups of G240 can be used to describe these feasible permutations. Specifically, we consider two limits of the molecular configurations. The equilibrium structure of H5+, i.e., [H2-H-H2]+, can be described using the G16 molecular symmetry group, while the dissociation products, i.e., H3+⋯H2, require the G24 molecular symmetry group. In the present study, a group theoretical analysis is performed for both limits, providing the symmetries for the nuclear spins and rovibrational wave functions. Also, spectroscopic properties for [H2-H-H2]+, particularly rovibrational couplings and electric dipole selection rules, as well as correlations of energy levels between [H2-H-H2]+ and H3+⋯H2, are obtained.