In this paper, on the 4th page (and throughout), they talk about studying electron-helium scattering in the "static-exchange approximation". I have scoured the literature and have not been able to figure out what this. There this power point which gives some really brief description but outside of that I can't figure out what it is. Apparently it is sometimes called the "continuum Hartree-Fock approximation". It seems like it gives a model of the potential that accounts for exchange effects in electron-atomic (or molecular) scattering. Can anyone give a self-contained explanation for this approximation?