Rovibrational excitation in collisions involving diatomic molecules

Abstract

The applicability of asymptotic series expansions of the type introduced by Gailitis (1976) in heavy particle scattering calculations is examined. The convergence of the solutions, with respect to the value of the scattering coordinate is found to be greatly improved in a model problem of the rovibrational excitation of H(_2) by H(^+). The results of infinite order sudden (IOS) and breathing sphere (BS) calculations of cross sections for the rovibrational excitation of (^12)C(^16)O by para- H(_2) (J(_1) = 0 only) are presented. Comparisons are made with existing theoretical and experimental results. Allowing for remaining uncertainties in the interaction potential of Poulsen (1982), our results are in reasonable accord with the experimental results of Andrews and Simpson (1976) for the vibrational relaxation of CO (v(_2) = 1) by ortho-H(_2). IOS calculations of the vibrational deactivation of (^12)c(^16)o (v(_2) = 1) by H(_2) (J(_1) = 0 or 2) which simultaneously undergoes the rotational transitions ΔJ(_1) = 0,2, or 4 are presented. Of major interest is the near-resonance process CO(Vb = 1) + H(-2) (J(_1) = 2) → CO (V(_2) = 0) + H(_2) (J(_1) = 6) + 87.03 cm(^-1) Comparison is made with both recent quantum mechanical and semi-classical calculations of this process, and with experiment. The near-resonance process is insufficient to account for the experimentally determined difference