Exchange Scattering of an Electron by the Hydrogen Atom

The theory of scattering of electrons by hydrogen has been re-examined with the objective of identifying the matrix element for the exchange scattered amplitude from the same integral equation which provides direct scattered amplitudes. The theory of Mott and Massey is verified, but it is demonstrated that their result contains contributions from the incident wave which must be removed before computing exchange amplitudes. The result is a theoretical justification for the Oppenheimer (prior) matrix element.