Elastic scattering of electrons by oxygen and nitrogen at intermediate energies

The total and differential elastic scattering cross section of electrons by atomic oxygen and nitrogen is calculated for energies between 1 and 500 eV in the distorted-wave (DW) approximation. The DW method has been modified by the inclusion of a polarization potential with an adjustable cutoff parameter which is determined variationally. The relative importance of polarization and exchange effects are compared for a variety of energies. These calculations show that the DW method is reliable above about 10 eV and with the inclusion of the polarization potential improves the estimates even below this energy.