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

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.