Quantification of plasmon excitations in core-level photoemission

Calculation of photoelectron spectra (PES) based on our previous dielectric response model [A. C. Simonsen et al. Phys. Rev. B 56, 1612 (1997)] for electronic excitations in PES are compared with recently reported experimental data. It is found that the dielectric description of electron energy losses in photoemission reproduces quantitatively the angular dependence of the surface and bulk electron losses observed experimentally for the Al2s photoemission spectra of Al(111), excited with MgKα radiation. The model also allows to calculate the separate intrinsic and extrinsic effects in photoemission. Thus, the extrinsic losses account for more than 95% of the total surface excitations. Regarding the bulk excitations, both extrinsic and intrinsic contributions vary significantly with emission angle. The intrinsic contribution represents ~35% of the intensity at the bulk plasmon position at normal emission while only 18% at 80^∘{} glancing emission. The calculations presented here can easily be used to interpret PES spectra of other materials in terms of intrinsic and extrinsic effects, if their dielectric properties are known.