The Calculation of Photoionization Cross Sections

Photoionization is a sensitive probe of many-body and spin-dependent interactions. One can test our understanding of these interactions and the role they play in atomic dynamics by comparing the results of theoretical calculations with corresponding experimental measurements. One finds from such comparisons that our understanding of the photoionization process in atoms is excellent in many cases, imperfect in many others, and inadequate in still others. One finds in general also that the kinds of many-body and spin-dependent interactions included in a calculation is, in many cases, a more important consideration than the particular calculational method employed. In this brief report we sketch those aspects of the photoionization process which are well understood as well as those which are not. We then comment on recent calculations for an eclectic assortment of atoms from throughout the periodic table. We close with remarks on some recent theoretical developments. No attempt at a definitive review of this growing field is made here. However, the situation up to about 1982 has been reviewed by the author elsewhere.