Effects on the x-ray spectra of metals due to final-state interactions with effective barriers and shape resonances

Model calculations of X-ray absorption, emission, and photoemission spectral lineshapes are reported for intrinsic and extrinsic core excitations in metals with final-state interactions that can be represented by a central attractive potential surrounded by an effective barrier on its periphery. Some of the calculated spectra exhibit novel features: XPS lineshapes with multi-electron shake-off sidebands and features characteristic of resonances and anti-resonances, and X-ray absorption and emission spectra with (i) edges that are apparently peaked (on a moderate energy scale) when the X-ray edge singularity causes them to be, in fact, suppressed on a fine scale, (ii) edges that are markedly rounded, and (iii) gross spectral features that are influenced greatly by the electronic structure of the iniial state of the Fermi sea, and only weakly by the final-state.