R-matrix calculation for electron-methane scattering cross sections

A recently developed technique for calculating cross sections in electron-molecule collision processes based on variational R-matrix theory is discussed. One of the main advantages of this method is its applicability to polyatomic systems. As a first example, integral and partial cross sections for the e^-+CH₄ system below the ionization limit and in the energy range of the Ramsauer minimum are presented. In addition, the corresponding eigenphases are shown. All calculations are based on the fixed-nuclei approximation. The paper is concluded by an analysis of the Ramsauer minimum with respect to the angular dependency of the differential cross sections in that energy region.