Electron—Alkali-Atom Interaction Potential and Elastic-Scattering Cross Section

Abstract

The potential energy between an incident electron and a neutral alkali atom has been calculated using first-order perturbation theory in the adiabatic approximation. The results are shown to be expressible in terms of a multipole expansion suitably generalized to allow for the penetration of the target-atom wave function by the incident electron. The monopole and dipole contributions have been calculated in detail for cesium. For large separations, the monopole contribution to the potential is small compared to the dipole contribution but becomes increasingly significant at smaller separations. For infinite separation, the calculations can be interpreted to yield the atomic polarizability, and the result for cesium (61.0 ${\mathrm{\AA }}^3$) is in reasonable agreement with experimental results. With this interaction potential, the elastic scattering of low-energy electrons from neutral cesium is treated in the adiabatic approximation with exchange. For purposes of comparison, the nonexchange approximation is also treated.