# Atomic Physics Workshop

Andrei V. Nefiodov, St. Petersburg Nuclear Physics Institute

Double photoeffect on inner-shell electrons

We review the recent progress in theoretical study of the double photoeffect on inner-shell electrons. The results have been obtained for heliumlike ions within the framework of QED perturbation theory, taking into account the leading orders of the $1/Z$ and $\alpha Z$ expansions. In the electric dipole approximation, the universal scalings can be obtained for the differential and total cross sections of the process under consideration. Going beyond the dipole approximation leads to a forward/backward asymmetry in the angular distributions for the ejected electrons with respect to the incident photon beam. We present also a comparison of our theoretical predictions for the ratio of double-to-single photoionization cross sections with available experimental data for a number of neutral atoms. Finally, we consider the time-reversed process of the correlated double-electron capture by a bare nucleus with emission of a single photon. Available theoretical results and experimental perspectives are discussed.