Polarization Potentials for Electron Scattering

Abstract

Charge polarization effects (due to polarization of the target charge distribution by the incident electron) are important for low and intermediate-energy electron scattering (these energy ranges corresponds to roughly E >~ IP and IP >~ E >~ 10 IP, where E is the impact energy and IP is the target ionization potential). There are two approaches to the inclusion of such polarization effects in electron scattering. In the many-body approach, the scattering wavefunction for the whole system (incident electron plus target) is represented explicitly by basis functions or products of basis functions and numerically determined radial functions. Algebraic variational methods2 and R matrix3 methods are some particularly powerful variants of this approach. In this approach charge polarization effects enter by configuration mixing. Because of this and because polarization effects are of long range, basis sets are required to be large and the scattering wavefunction must be represented over a big region. To avoid the associated computational problems, most electron-molecule scattering calculations using basis functions have been restricted to the single-configuration level, i.e., the static-exchange approximation, in which polarization effects are neglected.4