The characteristic energy of low-energy electrons in Ne, Kr, and Xe gases

Measurements have been made of the characteristic energy epsilon sub(k) = eD/μ (D: transverse diffusion coefficient; μ: mobility) of low-energy electrons in Ne, Kr, and Xe gases and in He/Ne gaseous mixtures by the Townsend method as a function of the reduced electric field E/N, where E denotes the field strength and N the number density of gas atoms. The momentum transfer cross section qsub(m) for electrons in Ne as derived from the data was found to be in excellent agreement with previous estimates obtained with different methods, particularly for energies ranging from 0.1 to 0.5 eV, and in fair agreement with any of the three theoretical results by Thompson, by Garbaty and La Bahn, and by Yau, McEachran and Stauffer. The characteristic energies obtained for Kr and Xe were both somewhat larger than the calculated values by Forst and Phelps and point to a sharper Ramsauer minimum in qsub(m) than reported by these authors. The data for He/Ne mixtures were explained fairly well by a calculation based on the Townsend method of average electrons. (Authors)