Elastic cross sections for e --CH4 collisions at intermediate energies

A joint theoretical and experimental investigation on e --CH4 elastic scattering in the intermediate energy range is reported. More specifically, calculated cross sections in the (1-SOO)-eV incident energy range, as well as measured absolute cross sections from 100 to 500 eV, are presented. A complex optical potential consisting of static, exchange, correlation-polarization, plus absorption contributions is used to describe the electron-molecule interaction. The Schwinger variational iterative method combined with the distorted-wave approximation is applied to calculate the scattering amplitudes. The experimental absolute elastic differential cross sections are determined using the relative flow technique. In general, our calculated results are in very good agreement with our experimental data and with other experimental and theoretical results available in the literature. Our study has shown the significant role played by the absorption effects on the calculated cross sections for incident energies of 50 eV and above. The importance of the nonspherical components of the e --CH4 interaction potential has also been verified in our calculations.