Momentum transfer cross sections for low-energy electrons in krypton and xenon from characteristic energies

Abstract

Characteristic energies of low-energy electrons in krypton and xenon gases have been measured at room temperature by the Townsend method as a function of reduced electric field. For both gases, observed characteristic energies were twice or even three times as large as the early estimates by Frost and Phelps (1964) based on the momentum transfer cross sections for electrons in these gases derived from drift velocity data. The cross sections were determined from the present experimental data over an energy range from 0.01 to 6.0 eV for krypton and from 0.01 to 5.0 eV for xenon. The minimum values and positions of Ramsauer minima in the derived cross sections were 1.0*10^-17 cm² at 0.5 eV for krypton and 4.0*10^-17 cm² at 0.6 eV for xenon. These minimum values are both definitely smaller than the previous experimental results of Frost and Phelps, while being rather close to, but still somewhat smaller than, those of Hoffmann and Skarsgard (1969). Theoretical cross sections calculated for krypton and xenon by Sin Fai Lam (1982) and by McEachran and Stauffer (1984) and those for krypton by Fon et al. (1984) all agree with the present experimental ones within +or-30% for energies below about 5 eV in both gases.