Vibrational–rotational relaxation from high vibrational states in He–HD

Abstract

The relaxation behavior of the He–HD system is studied by applying an exponential distorted wave procedure to calculate the cross sections and the rate constants for vibrational–rotational energy transfer in the vibrational manifolds n, 0⩽n⩽5. The rotational states are shown to play an important role in vibrational relaxation by providing many pathways for vibrational–rotational–translational energy exchange. By comparison with breathing sphere calculations it is demonstrated that the near exponential growth in the n→n−1 rates from vibrotor calculations can be attributed not only to the vibrational anharmonicity but also to the decreasing rotational energy spacings as n increases.