Theoretical description of the Fano-effect in the angle integrated valence band photoemission of paramagnetic solids

A theoretical description of the Fano-effect in the angle-integrated valence-band photoemission (VB XPS) of paramagnetic solids is presented that is based on the one-step model of photoemission and relativistic multiple scattering theory. Applications to fcc-Cu and fcc-Ag led to a very satisfying agreement with recent experimental data that show the Fano-effect, i.e., a finite spin polarisation of the photoelectrons is found for excitation with circularly polarised radiation. As can be demonstrated by model calculations, this finding is caused by the presence of spin-orbit coupling. To allow for a more detailed discussion of the spectra, a simplified description of the Fano-effect is presented that treats spin-orbit coupling as a perturbation.