Transverse diffusion of Li + ion swarms in Xe gas

Abstract

In our transverse diffusion measurements of Li+ ions in Xe gas, appreciable longitudinal end effects were found throughout the whole range of E/N (electric field to neutral gas number density ratio) studied, i.e. 5-150 Td. By applying a known linear relationship of the measured variance (x 2) of the transverse ion current density profile with drift length z, the magnitude a 2 of the end effects can be numerically derived. The ratio of the transverse diffusion coefficient to mobility, D T/K, at 309 K for the Li+-Xe system were eventually corrected for end effects by an analysis which requires measured (x 2) values and a 2. The value of a 2 is assumed to vary linearly with E/N. The corrected D T/K values are determined with an overall accuracy of +or-4%. The self-consistency and the good agreement of the results with those calculated by Monte Carlo simulations (MCS) bears evidence of the accuracy and reliability of the D T/K results. The accuracy of the MCS calculations is estimated to be +or-2.5%. The D T/K values for Li + in Xe were also derived using reduced mobility K 0 data obtained from the MCS calculations and from experimental data available in the literature, employing the generalized Einstein relations (GER) based on the three-temperature theory. © 1995 IOP Publishing Ltd.