Collection efficiency of photoelectrons injected into near- and supercritical argon gas

TL;DR

This study measures the collection efficiency of photoelectrons in dense argon gas near the critical temperature, revealing agreement with models at high fields but deviations at weak fields due to electrostriction effects.

Contribution

It provides new experimental data on electron collection efficiency near the critical point and highlights the influence of electrostriction on weak-field electron behavior.

Findings

High-field data agree with the Young-Bradbury model

Effective electron-atom scattering cross section can be deduced

Weak-field deviations are caused by electrostriction effects near criticality

Abstract

Injection of photoelectrons into gaseous or liquid dielectrics is a widely used technique to produce cold plasmas in weakly ionized systems for investigating the transport properties of electrons. We report measurements of the collection efficiency of photoelectrons injected into dense argon gas for $T=152.7 $K, close to the critical temperature $T_{c}\approx 150.9 $K, and for $T=200.0 $K. The high-field data agree with the Young-Bradbury model and with previous measurements below $T_{c}$ and at an intermediate temperature above $T_c .$ The effective, density-dependent electron-atom momentum transfer scattering cross section can be deduced. However, the weak-field data near $T_{c}$ show large deviations from the theoretical model. We show that the electron behavior at weak field is influenced by electrostriction effects that are only important near the critical point.