Vibration–translation energy transfer in anharmonic diatomic molecules. II. The vibrational quantum-number dependence

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Abstract
A semiclassical model of the inelastic collision between a vibrationally excited anharmonic oscillator and a structureless atom is used to predict the variation of thermally averaged V–T rate coefficients with temperature and initial-state quantum number. Multiple oscillator states are included in a numerical solution for collinear encounters. The results are compared with CO–He experimental values for both ground and excited initial states using several simplified forms of the interaction potential. The numerical model is also used as a basis for evaluating several less complete but analytic models. Two computationally simple analytic approximations are found that successfully reproduce the numercial rate coefficients for a wide range of molecular properties and collision partners. Their limitations are also identified. Finally, the relative rates of multiple-quantum transitions from excited states are evaluated for several molecular types.