Classical differential cross sections and rotational energy transfer distributions for realistic ion—molecule potentials in the CPST limit

Abstract

Classical differential cross sections, rotational energy transfer distributions at specified scattering angles and the first moments of the rotational energy transfer distributions are calculated for two ion—molecule systems: K + −CSCl and Li + −CO. The deflection angles and change in angular momentum are calculated using classical perturbation scattering theory (CPST). Monte Carlo techniques are then used to calculate the orientation averaged total differential cross sections and the rotational energy transfer distributions. Results are compared with experiment and agreement is found to be satisfactory. These two systems represent two extremes in anisotropy. For Li + −CO a strong classical rainbow peak is still seen in the differential cross section, while in the K + −CSCl system the rainbow is complete quenched. In the rotational energy transfer distributions of both systems, rotational rainbow peaks are clearly observed. The calculations also predict a leveling off of the first moment of the rotational energy transfer distribution at high angles, corresponding to the transition to repulsive scattering. On the basis of these results some comments are made on the nature of classical rainbow scattering for anisotropic systems.