The effects of collision energy and vibrational excitation on H+2, HD++He reactions

Abstract

An experimental study of proton and deuteron transfer in H⁺₂ + He and HD⁺ + He has been carried out as a function of kinetic and vibrational energy. The data gives evidence that at lower kinetic energies, the spectator stripping mechanism indeed plays an important role when H⁺₂ or HD⁺ is vibrationally excited. The H⁺₂ (v=0) reaction has a much smaller cross section than the v=1–4 reactions and seems to go through intimate, small impact parameter collisions involving all the atoms. Investigation of the competition between both the proton and deuteron transfer channels for the HD⁺ case, shows that vibrational enhancement towards forming the HeD⁺ product falls off sooner with increasing kinetic energy than does the HeH⁺ product again in accordance with the spectator stripping model. The higher yield for HeH⁺ production at both higher vibrational levels of HD⁺ and at lower kinetic energy and the behavior of translational energy dependence of HeH⁺ seems to indicate the importance of the induced orientation of HD⁺ during the collision with He. Because of the displacement of the center of mass from the center of charge in HD⁺, the charge induced dipole interaction between He and HD⁺ tends to swing the H atom more towards He during the approach of He and HD⁺.