Coupled three-dimensional quantum mechanical wave packet study of proton transfer in H₂⁺ + He collisions on accurate ab initio two-state diabatic potential energy surfaces

Abstract

We have carried out fully close-coupled three dimensional quantum mechanical wave packet dynamical calculations for the reaction He+ H₂⁺→HeH⁺+H on the ground electronic adiabatic potential energy surface and on the lowest two electronic states of newly constructed ab initio calculated diabatic potential energy surfaces for the system. With the reactant diatom (⁠H₂⁺⁠) in its roto-vibrational ground state (v = 0, j = 0), the calculations have been carried out in hyperspherical coordinates to obtain the reaction attributes. Convergence profiles of the reaction probability with respect to the total angular momentum quantum number at different collision energies are presented for the title reaction. State-to-state as well as initial state selected integral reaction cross sections are calculated from the fully converged reaction probabilities over a range of collision energies. The integral cross section values computed using the two-state diabatic potential energy surfaces are significantly lower than those obtained using the ground electronic state adiabatic potential energy surface and are in much better agreement with the available experimental results than the latter for total energy greater than 1.1 eV. Therefore, it becomes clear that it is important to include the nonadiabatic coupling terms for a quantitative prediction of the dynamical observables.