Rotational-level mixing and intracollisional interference in the pure rotational spectrum of HD gas

Rotational-level mixing by anisotropic intermolecular forces is found to be important to the mechanism which produces intracollisional interference effects in the pure rotational spectrum of HD and HD--inert-gas mixtures. The major contribution involves the anisotropic repulsive term in the potential and the anisotropic overlap-induced dipole moment. Improved agreement between calculation and experiment results when the mixing is included in the analysis.