A comparative account of quantum dynamics of the H⁺ + H₂ reaction at low temperature on two different potential energy surfaces

Abstract

Rotationally resolved reaction probabilities, integral cross sections, and rate constant for the H⁺ + H₂ (v = 0, j = 0 or 1) → H₂ (v′ = 0, j′) + H ⁺ reaction are calculated using a time-independent quantum mechanical method and the potential energy surface of Kamisaka et al. [J. Chem. Phys.116, 654 (2002)] (say KBNN PES). All partial wave contributions of the total angular momentum, J, are included to obtain converged cross sections at low collision energies and rate constants at low temperatures. In order to test the accuracy of the KBNN PES, the results obtained here are compared with those obtained in our earlier work [P. Honvault et al. , Phys. Rev. Lett.107, 023201 (2011)] using the accurate potential energy surface of Velilla et al. [J. Chem. Phys.129, 084307 (2008)]. Integral cross sections and rate constants obtained on the two potential energy surfaces considered here show remarkable differences in terms of magnitude and dependence on collision energy (or temperature) which can be attributed to the differences observed in the topography of the surfaces near to the entrance channel. This clearly shows the inadequacy of the KBNN PES for calculations at low collision energies.