A Reevaluation of the Diatomic Processes Leading to CH and CH+ Formation in the Interstellar Medium

We have reevaluated the direct radiative recombination coefficients for CR and CR + using recent atomic and molecular data in a purely quantum-mechanical matrix-scattering formalism. The resulting coefficients are appreciably smaller than the classical values of Bates. Indirect radiative recombination can occur through preassociation with rates comparable to those we find for CR and CR+ for the direct process. Photodestruction for CR and dissociative recombination for CR + appear dominant in limiting their respective abundances. Our calculated column densities fall short of the observed column densities in Oph, although purely diatomic processes could account for about one-quarter of the CR + if the rate for dissociative recombination has been overestimated. Subject headings: interstellar matter - molecules - molecules, interstellar