The Li+–He interaction potential

Abstract

New measurements of the mobility of Li⁺ ions in He gas at 300°K are reported for a wide range of E/N, the ratio of the electric field strength to the gas number density. These data are used in conjunction with kinetic theory to test various Li⁺–He interaction potentials over a wide range of separation distance. It is shown that the ab initio potential of Hariharan and Staemmler gives mobility values in excellent agreement with experiment at low and moderate E/N, but that significant discrepancies exist at high E/N. The mobility data are also directly inverted to give the Li⁺–He interaction potential. This directly determined potential is in excellent agreement with the ab initio at intermediate and long range, but differs significantly in the short‐range region. In the latter region, however, it is in agreement with the potential obtained by analysis of beam‐scattering experiments.