A perturbative treatment of classical vibrational-translational energy transfer in collinear collisions of an atom and a diatomic molecule

An analytical expression is derived for average vibrational energy lost or gained [Delta E-v] per collinear collision of an atom and a diatom. The der ivation, based on classical mechanics, uses the perturbative method of the variation of constants and is valid in the weak coupling limit. Second-orde r results for [Delta E-v] are obtained in terms of power spectra of the unc oupled vibrational and translational degrees of freedom. The classical resu lts are compared to perturbative quantum calculations, and differences betw een the two are described. (C) 1999 Elsevier Science B.V. All rights reserv ed.