Potential energy surfaces of the reaction C++H2 → CH++H

Potential energy surfaces of six low lying states for the reaction C++H2 have been calculated with an ab initio MCSCF–POLCI method. An emphasis has been placed on the reaction channel leading to the chemiluminescent product CH+(A 1Π)+H(2S). Based on the characteristics of the surfaces, a mechanism for this reaction has been proposed which involves a nonadiabatic transition from 2 2A′ to 3 2A′ in the vicinity of the C2v symmetry. An alternative path involving a 1 2A″ → 2 2A″ transition cannot be denied.