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 (x2) of the transverse ion current density profile with drift length z, the magnitude a2 of the end effects can be numerically derived. The ratio of the transverse diffusion coefficient to mobility, DT/K, at 309 K for the Li+-Xe system were eventually corrected for end effects by an analysis which requires measured (x2) values and a2. The value of a2 is assumed to vary linearly with E/N. The corrected DT/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 DT/K results. The accuracy of the MCS calculations is estimated to be +or-2.5%. The DT/K values for Li+ in Xe were also derived using reduced mobility K0 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.