Ionization of an atom by photoabsorption at high photon energies: unified view in terms of singularities of the Coulombic potentials

Abstract

We discuss a unified nonrelativistic approach to single and multiple ionization of atoms by absorption of a photon of high incident energy ω (but still ω⪡ m). The approach is based on asymptotic Fourier transform theory (AFT), modified by Coulombic interactions. The AFT theory connects the high energy behavior of photoabsorption matrix elements with the singularity structures of the inter-particle Coulomb interactions and takes into account initial and final state correlation. The modification of this AFT result by Coulombic interactions leads to a rapid convergence of cross sections with photon energy. We illustrate these ideas for the simple example of photoionization in a potential and then discuss its generalizations.