Potential surface dependence of vibrationally inelastic collisions between He and H2

Publisher Website
Google Scholar
Abstract
We have carried out a careful study of He–H2 vibrationally inelastic collisions based on five different analytic fits to the Gordon-Secrest [J. Chem. Phys. 52, 120 (1970)] ab initio interaction potential. Within a model which freezes the atom-diatom orientation, we solve the collision dynamics fully quantum mechanically. Both for the 0→1 and 3→4 vibrational transitions, we find that the use of different analytic surfaces leads to substantial qualitative and quantitative differences in the calculated transition probabilities. In particular, we observe an anomalous angular dependence in the case of the original Gordon-Secrest analytic surface. We show that this arises from difficulties in the extrapolation of the ab initio points in the classically forbidden region at small center-of-mass separation. These results have important implications for future theoretical study of molecular collisions.