Photoionizaion of Atoms Near Inner Shell Thresholds

Abstract

It is demonstrated that photoionization of atoms near inner shell thresholds is in essence a multielectron process which is determined to a large extent by interelectron interaction. The mechanisms of multiple ionization are discussed, including not only Auger-decay chains but shake-off, direct knock-out and ground-state correlations. The frequency dependence of the mean ion charge near inner shell threshold is obtained. Simple formulae are presented describing Post Collision Interaction photoelectrons’ energy shift accompanying multi-step Auger-decay of an inner vacancy. Some peculiarities of an inner-shell discrete excitation are analyzed. Possible mechanisms of single charge ion production are considered. The paper emphasizes that photoionization near inner shell thresholds, particularly for heavy atoms, is an intriguing process, affected by different mechanisms of multielectron correlations.