Quantum studies of inelastic collisions of NO(X 2Π) with Ar

Abstract

Coupled-states (CS) and close-coupling (CC) calculations for collisions of NO(X 2Π) with Ar are reported, based on the potential surface of Nielson, Parker, and Pack [J. Chem. Phys. 66, 1396 (1977)]. The CS approximation is shown to be accurate and was used to generate converged cross sections at total energies of 0.035, 0.0555, and 0.0708 eV. Comparison with CS cross sections, obtained by neglecting the spin and electronic orbital angular momentum of the molecule, indicate that this neglect can introduce substantial error. At low J, the calculated cross sections are unaffected by inclusion of the spin-rotation coupling terms in the molecular Hamiltonian. Both for transitions within the Ω=1/2 spin-orbit manifold and for Ω=1/2→3/2 transitions we find good qualitative agreement with the relative J→J′ cross sections, summed over the Λ doublets, determined experimentally by Joswig and Andresen [J. Chem. Phys. 77, 2204 (1982), and to be published]. In particular the Ω=1/2→3/2 cross sections are about an order of magnitude smaller than the cross sections for transitions within the Ω=1/2 manifold and also show an increase with increasing ΔJ, contrary to what is usually seen in rotationally inelastic collisions. For transitions within the Ω=1/2 and Ω=3/2 manifolds, the sudden limit propensity rules and scaling relations derived earlier [J. Chem. Phys. 76, 5974 (1982)] are validated, and a new propensity rule established. By contrast, the sudden limit propensity rules and scaling relations appear to be of poor accuracy for transitions between the two spin-orbit manifolds.