Equivalent exchange potentials in electron scattering

A number of local potentials have been suggested to represent the non-local exchange kernel in electron-atom scattering. A comparative numerical study has been made in which phase shifts for the elastic scattering of electrons by H, He+ and He using these potentials are tested against those calculated from the exchange integro-differential equations. The influence of additional long range polarization potentials is also investigated. It is shown that, except at the lowest energies, exchange effects can be represented accurately by the Furness-McCarthy and related potentials.