Rotational cooling of HD+ molecular ions by superelastic collisions with electrons

Abstract

Merging an HD+ beam with velocity matched electrons in a heavy ion storage ring we observed rapid cooling of the rotational excitations of the HD+ ions by superelastic collisions (SEC) with the electrons. The cooling process is well described using theoretical SEC rate coefficients obtained by combining the molecular R-matrix approach with the adiabatic nuclei rotation approximation. We verify the ΔJ=-2 SEC rate coefficients, which are predicted to be dominant as opposed to the ΔJ=-1 rates and to amount to (1-2)×10-6cm3s-1 for initial angular momentum states with J≤7, to within 30%. © 2009 The American Physical Society.