Theory of (e, 2e) reactions

A comprehensive survey is given of the theory of (e, 2e) reactions. We begin by discussing the kinematics of these reactions, with special attention devoted to the coplanar asymmetric (Ehrhardt-type) geometry and the fully symmetric geometry in which most of the recent (e, 2e) coincidence measurements have been performed. We then review the foundations of the theory of the ionization of atoms by electron impact, first for one-electron atoms and then for target atoms with N electrons. Next, we discussed the Wannier theory of threshold ionization and its excitations. We then turn to the analysis of (e, 2e) reactions at intermediate and high energies. The theory of fast coplanar asymmetric (e, 2e) reactions is analyzed and it is shown that the eikonal-Born series method successfully accounts for all the dynamical features of these reactions. In particular, it is shown that second order effects are essential in explaining all the features exhibited by the measured by the measured triple differential cross sections at intermediate energies. Finally, we review the theory of fast symmetric (e, 2e) reactions. We consider first the (e, 2e) spectroscopy regime in which the momentum transfer Δ is large, but the recoil momentum Q of the ion is small or moderate. We then turn to the regime of large Δ and large Q, for which second order effects are of paramount importance, so that the coplanar symmetric triple differential cross section exhibits a striking behaviour in the large angle region. © 1989.SCOPUS: re.j