Thermodynamic Model for the Oxygen Ion Mobility in Dense Argon Gas

TL;DR

This paper presents experimental measurements of O extsubscript{2} extsuperscript{−} ion mobility in argon gas across various densities and temperatures, highlighting the limitations of traditional theories and the success of the free volume model.

Contribution

It introduces the application of the free volume model to describe ion mobility in dense argon gas, where conventional theories fail.

Findings

Kinetic and hydrodynamic theories do not fit the data at intermediate densities.

The free volume model accurately describes the experimental mobility data.

The model previously successful in neon and helium also applies to argon.

Abstract

We report experimental data of the mobility of O\(_2^-\) ions in argon gas as a function of the density in the temperature range between \(180\,\mbox{K}\le T\le 300\,\mbox{K}\). At the intermediate, though fairly large, densities of the experiment both the kinetic theory and the hydrodynamic theory fail at describing the experimental data. By contrast, the free volume model, originally developed to describe electron and ion mobility in superfluid helium, gives a satisfactory agreement with the data as previously obtained for the O\(_2^-\) ion mobility in both dense neon and helium gases.