Multielectron inner-shell photoexcitation in absorption spectra of Kr : theory and experiment

The probability of Kr 1[ital s] photoionization alone and accompanied by 4[ital p], 3[ital d], 3[ital p], 2[ital s], and 2[ital s]4[ital p] excitations has been calculated as a function of photon energy in the vicinity of the respective thresholds; pertinent energies have been computed including relativistic, quantum-electrodynamic, and relaxation effects. Sharp features from two-electron excitations are expected in absorption spectra only if at least one of the electrons undergoes a transition to a bound state; this becomes less probable in inner shells. An absorption-spectrometry experiment on Kr has been performed with synchrotron radiation; results generally confirm the predictions but also point toward refinements that are required in the theory and the need for improvements in techniques and synchrotron-radiation sources.