A comparative nearside-farside analysis of the He–N₂ ⁺ and He–N₂ inelastic collisions

Abstract.

A comparative study of the inelastic scattering of ¹⁴N₂ ⁺ and ¹⁴N₂ in collision with ³He atoms is presented. The unrestricted nearside-farside (NF) method proposed by Connor [J. Chem. Phys. 104, 2297 (1995)] is applied to analyse the Close Coupling rotationally state selected angular distributions for four kinetic energies. These four energies illustrate different regimes of the dynamics. The relationships between the structures of the calculated differential cross-sections (DCS) and the different regions of the potential energy surfaces involved which can be extracted from semi classical models are here easily obtained from a simple reading of the (NF) figures. At the higher energy far-off the wells (1000 cm^-1) the shape of the DCS are quite similar for the two systems and their nearside-farside components also, showing that the inelastic process is controlled by the short range repulsive part of the potential which is essentially the same for these two collisions. When the energy is decreased the differences between the two wells associated with the He–N₂ ⁺ and He–N₂ complexes are responsible for the differences between the DCS for the two systems. The farside component associated with the well become more and more prominent for the elastic scattering while inelastic scattering remains controlled by the repulsive core in a large angular interval. The nearside farside analysis gives also a new picture of a resonance which is regarded as an equilibrium between the repulsive and the attractive parts of the potential.