Vibrational Excitation of Polar Molecules by Slow Electrons: HCI

Abstract

Shape resonances cannot explain the strong vibrational excitation observed in the impact of electrons on polar molecules at threshold, because an important $s$-wave component in the wave function inhibits trapping. We explain the main features observed in HCl by invoking the concept of a virtual state to account for an enhancement of the wave function of a slow departing electron.