Electron shake-up and correlation satellites and continuum shake-off distributions in X-Ray photoelectron spectra of the rare gas atoms

Abstract

The rare gases H, He, Ne, Ar, Kr and Xe have been studied in the gas phase at low pressure by means of high resolution photoelectron Spectroscopy. Monochromatized Al Kα radiation at 90° was used to excite the photoelectrons. Extended energy regions of all valence electron spectra and the most interesting core electron spectra have been recorded. The spectra contain a large number of correlation satellites and shake-up as well as double shake-up satellites which originate from unknown highly excited, singly ionized states. The energies and intensities of these discrete satellites have been determined and several states are identified. The assignments rely partly on results from relativistic MCSCF calculations, and partly on comparisons with optical data and recent Auger electron data. Relativistic MCSCF energies for a large number of excited states in Kr + and Xe + are reported. Extended shake-off continua in both the valence region and in the core electron regions have been recorded. The shake-off continua of Ne and Ar reveal several Fano-like resonance states. The resonances occur when shake-up photoionization channels, involving inner valence electron excitation or multiple valence excitation, have the same energies and symmetries as photoionization channels for outer valence electron shake-off. A theoretical model for this type of resonance is presented and some numerical results are obtained and compared with experimentally determined Fano parameters for the most prominent resonance in the Nels shake-off spectrum.