Electron ionization and excitation coefficients for argon, krypton, and xenon in the low E/N region

Abstract

The electron ionization coefficients for Ar, Kr, and Xe have been measured in the low E/N region [(0.5–4) ×10−16 V cm2] using a drift-tube apparatus. At low field values, the ionization coefficient was found to be anomalously large, a fact attributed to surface photoelectron emission from radiating metastables. This contribution also explains the discrepancy between earlier measurements and recent calculations based on the transport equation. The measurements were analyzed on the basis of two contributions to the ionization rate and calculations of the transport equation, yielding a revised set of inelastic cross sections which differ from earlier ones primarily in the inclusion of shape resonances.