Abstract
Using a quantal many‐body theory of hyperthermal atom–polyatomic collisions, we present a detailed study of the role of intramolecular dynamics in vibrational energy transfer. In this approach, differential vibrational cross sections are given by time‐correlation functions (TCFs) of the motions of the target atoms. Slow rotations of polyatomic molecules are decoupled from vibrations, and we concentrate on vibrational energy transfer. The dependence of the TCFs on collision energy, scattering angle, and changes in vibrational quantum numbers is examined in detail for a general polyatomic, and it is shown how each target atom contributes to vibrational energy transfer. For the systems Li+/CO2 and Li+/N2O, we present vibrational differential cross sections calculated with new multicenter short‐range potentials obtained from the uniform electron‐gas model. Comparison of theoretical results with experimental measurements of the Li+/CO2 system shows good agreement for several collision energies and scattering angles. Furthermore, we show how the structure of the vibrational cross section is related to the atomic parameters of the target and to the relative sizes of the repulsive cores of the intermolecular potential.