We summarize models applied for interpretation of photoelectron emission spectra. The models are compared and the validity is discussed by comparison to various sets of experiments.
It is found that the two step model gives a reasonable description of the rough processes. However the more detailed effects are only well described by a one-step model which includes effects of the core hole and of the surface. It is found that the semiclassical dielectric response model gives a fairly good quantitative description.
Finally a new correction parameter is discussed which takes into account the effects of the core hole and the surface excitations. This is similar to the surface excitation parameter used in REELS but is different due to the presence of the core hole.