Polarization and Exchange Effects in Slow-Electron Scattering from Lithium and Sodium

Abstract

Total elastic-scattering cross sections have been calculated for low-energy electrons incident on lithium and sodium. The effects of target distortion by the electric field of the incident particle and electron exchange between incident and bound electrons have been included through the "adiabatic exchange" approximation. In this method, the effect of the distortion induced in the target atom is computed through a polarization potential which is obtained by the method of polarized orbitals. The phase shifts and the total elastic-scattering cross sections are obtained through the solution of a set of integrodifferential equations. The calculated polarization potential agrees asymptotically with experimental determinations of the dipole polarizability of Li and Na, and the total elastic-scattering cross sections agree well with recent measurements over the entire experimental range. Results for both alkalis exhibit a small resonance at the experimental peak around 1 V and a second peak at lower energies outside the present experimental range.