Direct Chemical Dynamics Simulations of H₃⁺ + CO Bimolecular Reaction

The proton transfer reaction H₃⁺ + CO → HCO⁺/HOC⁺ + H₂ has gained considerable attention in the literature due to its importance in interstellar chemistry. The reaction products-formyl cation (HCO⁺) and isoformyl cation (HOC⁺)-are known to initiate multiple chemical reaction networks, resulting in complex molecules found in space. Several experimental and theoretical studies probing the structure and energetics of the [H₃CO]⁺ system, HCO⁺/HOC⁺ product branching ratios, reaction mechanisms, etc., have been reported in the literature. In the present work, we investigated the H₃⁺ + CO bimolecular reaction in the gas phase using direct dynamics methodology. The simulation conditions were chosen to mimic recently reported velocity map imaging experiments on the same reaction. The calculations were performed using the density functional PBE0/aug-cc-pVDZ level of electronic structure theory. Internal energy and scattering angle distributions of reaction products found from the simulations are in qualitative agreement with the experiment. However, the product branching ratios at low collision energies were in contrast with the experimental predictions. Interesting dynamical features were observed in the simulations, and detailed atomic level mechanisms are presented.