The mobilities of ions in unlike gases

Abstract

The available experimental data on the mobilities at low field strengths of ions in unlike gases are analyzed on the basis of a simple theoretical description. Some of the earlier conclusions are modified and the current discrepancies between theory and experiment are emphasized. It is shown that most of the measurements can be explained by classical theory on the assumption that the interaction between an ion and a gas particle is due to the polarization of the gas particle, but that there appears to be a consistent discrepancy of about 8 % between theoretical predictions and the series of measurements by the Bristol group. For gases of low polarizability or at high temperatures, the contribution of the repulsive forces must be considered and the case of Li+ in He is investigated in detail, an interaction being derived from which the observed variation of mobility with temperature may be reproduced.