Collisional excitation of very high rotational levels of HF in small angle scattering with He⁺ at E_lab=25-50 eV

Abstract

Energy loss distributions of He⁺ ions after collisions with HF molecules in a secondary beam at laboratory collision energies in the range 25-50 eV show a regular structure indicating rotational excitation up to ΔJ=35 with no clear evidence for vibrational excitation. The observed propensity for large ΔJ transitions decreases with increasing collision energy but increases with increase in scattering angle. Three dimensional quasiclassical trajectory calculations using a potential energy surface based on the He⁺-Ne interaction at short range and a damped long range ion-dipole (quadrupole) interaction reproduce all the essential features of the experimental results.