Many-body calculations of photoionization cross sections

Abstract

The calculation of photoionization cross sections of atoms is discussed in the framework of many‐body perturbation theory. The use of appropriate coupled equations allows the summation to infinite order of certain classes of diagrams and can account for resonance structure in the cross sections. The calculations are carried out using complete sets of single‐particle states with discretization of the continuum. Examples are given for the process of photoionization with excitation for helium and argon atoms. The cross section of atomic tungsten is calculated as an example of a complex, open shell atom. As an example of an alternative method, an extensive R‐matrix calculation for the 1s photoionization cross section of beryllium is presented.