Low energy dependence of momentum transfer rate constants of rare gas atomic ions in their parent gases: Evidence for the importance of a polarization potential at near thermal energies

Abstract

The total momentum transfer rate constants k m for rare gas atomic ions in their parent gases have been measured versus ion energy from ∼0.3 eV to 1.1 eV(He +), 4.3 eV(Ne +), 1.5 eV(A +), 0.6 eV(Kr +) and 0.5 eV(Xe +). The measurements were made by an ion cyclotron resonance collisional line broadening method. For all the rare gases it was found that k m initially decreases with increasing ion energy, passes through a minimum near 0.5 eV and then increases with ion energy. From a consideration of the relation of the interaction potentials of ion—atom systems with the energy dependence of the total momentum transfer rate constant, we conclude that the initial decrease in k m with ion energy indicates the importance of a polarization potential coupled to a repulsive and/or a charge exchange potential.