Double photoionization near the inner-atomic shell threshold: dynamics of two-electron emission

The double-electron ejection process after photon absorption by an atom is considered near the inner-atomic shell threshold. The aim of our work is to clarify the dynamics of double-electron emission. For this purpose, it is of primary importance to investigate processes with well-defined final ionic states. The focus of our study in this case is resonant reactions with a low energy for one electron, whereas the energy of the other one is close to the energy of the Auger electron. In this case, important contributions to the cross section of three different processes have to be considered: (1) photoionization of the inner shell followed by Auger decay of the inner vacancy influenced by post-collision interaction (PCI); (2) the PCI capture of the slow photoelectron into a discrete state followed by valence multiplet decay, and (3) the double photoionization of the outer shell. A quantum-mechanical approach has been developed to take into account the contribution to the cross section of amplitudes of all three processes. This model is applied to the case of double photoionization of the Kr atom near the 3d-shell threshold. Our calculation predicts an interference effect in the channel of the 1D final state, whereas in the 3P final state channel the role of interference is negligible.