Rotationally inelastic scattering of OH(2Π) by HCl(1Σ). Comparison of experiment and theory

Abstract

State-to-state integral cross sections were calculated using quantum open-shell and closed shell close coupling scattering calculations and quasi-classical trajectory calculations. Reduced dimensionality calculations for the OH–HCl system are compared to those for the OH–Ar system. We have explored the sensitivity of the cross section to the nature of the PES, using either a two-dimensional or a four-dimensional PES. Only the diagonal diabatic V_sum potential was used in the calculations and therefore the electronic fine structure, i.e. the spin–orbit and Λ-doublet structure, could not be accounted for. All the calculations were performed for the same collision energy of 920 cm⁻¹ and assuming that initially all OH molecules are in the lowest rotational state, J = 3/2, Ω = 3/2. The theoretical results are discussed in comparison with the experimental data measured under similar conditions. The agreement of experimental results with the theoretical model based on four-dimensional close coupling calculations and treating the OH molecule as a closed-shell species is good. The validity of different proposed correspondence schemes for the transitions in OH considered as a closed-shell and as an open-shell molecule is examined by comparing the cross sections obtained for the OH + Ar system and the two-dimensional model for the OH + HCl system.