Theoretical studies of rotationally inelastic collisions of molecules in ³σ electronic states: O₂(X³σ_g^-) + He

Abstract

Rotationally inelastic collisions of a ³σ-state molecule have been treated by both the accurate quantum close-coupling formalism and the coupled-states approximation. Cross sections are reported for the O₂ + He collisions at room temperature for the experimental potential surface of Faubel et al.

The effect of appropriate angular momentum coupling scheme is discussed. Calculations are performed in the conventionally used Hund's case (b) coupling and in an intermediate coupling between Hund's cases (a) and (b). A remarkable departure from Hund's case (b) is found, particularly for cross sections involving low J.

The computed cross sections reveal several propensity rules characteristic for rotational energy transfer in ³σ molecules.

The coupled-states approximation is found to be in a good quantitative agreement with the close-coupling results.