Study of the isotropic contribution to the analysis of photoelectron diffraction experiments at the ALOISA beamline

The angular distribution of the intensity in photoemission experiments is affected by electron diffraction patterns and by a smoothly varying contribution originated by both intrumental details and physical properties of the samples. The peculiar variety of scattering configurations available at the ALOISA beamline experimental station in Trieste stimulated the developement of an analytical description for the smooth angular dependence sustaining the diffraction features. We present here the basic formulae and their application to experimental data taken on the Fe/Cu(3)Au(001) system in order to highlight the role of the various parameters included in the distribution function. A specific model for the surface illumination has been developed, and the overlayer thickness and surface roughness have been considered.