Inelastic collision cross sections of CH(X 2Π) with He(1S) on new ab initio surfaces

Abstract

Full close-coupled (CC) integral inelastic cross sections were determined for collisions between CH(X 2Π)(N′=1) and He. These calculations are based on new ab initio CEPA (coupled electron pair approach) potential energy surfaces computed by Abdallah et al. These theoretical CC cross sections confirm a previous prediction of preferential population of final states levels in which the electronic wave function of the CH molecule is antisymmetric with respect to reflection in the plane of the molecule. These results are compared with the experimental results of Macdonald et al. At all energies the discrepancies were in most cases less than 7% of the ratio of the sum of the cross sections for the four transitions into levels of nominal A″ reflection symmetry divided by the sum of the cross sections for the four transitions into levels of nominal A′ reflection symmetry. Nevertheless, there is substantial disagreement in the magnitudes of the ratios particularly for the transitions with larger inelasticity.