Dynamics of the C+–H2 reaction

Abstract

The reaction of C+(H2, H)CH+ and its isotopic variants have been investigated by measuring the velocity vector distribution of product ions formed when a collimated, energy selected beam of C+(2P(1/2)) impinges on a target gas. At relative energies below 4 eV, the reaction product velocity distribution shows a high, but not perfect, degree of symmetry in the barycentric system. The nonreactively scattered C+ shows a very inelastic component in addition to elastic features. The form of the distributions suggests that in many collisions, the system passes through configurations in which all three atoms interact strongly for times which are of the order of one rotational period. At higher relative energies, the product distributions are consistent with a direct interaction mechanism, but indications of strong three-body interactions remain. The behavior is consistent with the electronic state correlation diagram for the system, which shows that the deep (4 eV) potential well of symmetric CH2+ is accessible to the reactants and products.