Momentum-Transfer Cross Sections and Conductivity Ratios for Low-Energy Electrons in He, Ne, Kr, and Xe

Abstract

Conductivity ratios have been measured in weakly ionized afterglows of repetitively pulsed, electrodeless, rf discharges in helium, neon, krypton, and xenon using a microwave resonant cavity (2.7 GHz). Maxwellian electron-energy distributions were obtained at temperatures from 300\ifmmode^\circ\else\textdegree\fi{}K to 10 000\ifmmode^\circ\else\textdegree\fi{}K, as measured with a gated microwave radiometer (4 GHz), Momentum-transfer cross sections for electrons of energy up to 2 eV in neon, krypton, and xenon were determined from the measured conductivity ratios by an iterative procedure. The results in helium support the momentum-transfer cross section determined from the electron-beam experiments of Golden and Bandel. Those for neon indicate a scattering length of $+0.20{a}_{0}$. The momentum-transfer cross sections for krypton and xenon agree best with, but are generally lower than, those of Frost and Phelps and indicate a deeper (approximately 2.5 times) Ramsauer minimum. An experimental check of the theoretical electron-ion collision frequency for high-frequency, low-temperature conditions has been made.