Precision studies of deep-inner-shell photoabsorption by atomic ions

Abstract

With emphasis on K-shell ionization and K-shell excitation mediated by the absorption of a single photon the present paper provides an overview of the status of experiments in which deep-inner-shell photoabsorption by atomic ions has been investigated. For inner-shell processes not involving the K-shell only photon energies beyond about 350 eV are considered. Mechanisms of photoabsorption and subsequent relaxation as well as relations between photoionization and photorecombination are discussed. New possibilities for precise measurements of transition energies have been provided by the high photon-energy resolution available at 3rd generation synchrotron light sources. This is particularly interesting for studies of K-shell excitation of few-electron systems. By using atomic ions as targets, either in form of a collimated beam or trapped in electromagnetic fields, it has been possible to reach a high level of precision in the spectroscopy of transitions involving the decay of K vacancies by photoemission or Auger processes. Examples for absolute cross section measurements and precision spectroscopy are presented.