Scattering of electrons by CH₄, CF₄and SF₆in the 75-700 eV range

Abstract

Differential cross sections (DCS) have been measured by the crossed-beam method. The angular range is 5-135' and the electron energies are 75, 100, 150, 200, 300, 500 and 700 eV. The overall energy resolution is not sufficient to discriminate elastic scatterings from rotational and vibrational excitations. The absolute DCS are determined by using a gas chamber on the basis of the known absolute DCS for He. The experimental DCS are extrapolated to 0' and 180' scattering angles by fitting the square of the Legendre polynomials to the measured values. The integral and momentum transfer cross sections are then obtained. The errors are about 10% for all experimental results. The present data for CH4 agree well with the previous measurements and calculations. For CF4 and SF6, the DCS increase steeply at the forward angles. The integral cross sections obtained are consistent with the previous results for total and inelastic cross sections.