The differential cross section for electron-impact ionization of atoms has been derived for the general case and the dipole ($E1$) limit of the Born approximation. Emphasis was placed on the theoretical description of the ($e$,$2e$) angular correlation between fast electrons scattered in the forward direction and electrons ejected by the ionization process. The general angular-momentum treatment of this work results in a more complete description of the dipole ($e$,$2e$) angular distribution than previous purely kinematic analyses.

• Received 14 April 1982

DOI:https://doi.org/10.1103/PhysRevA.26.1907