Parameterization of HAXPES photoelectrons with kinetic energies up to 10Â keV

An algorithm for modeling transport of photoelectrons with kinetic energies up to 10 keV has been developed. Calculations were performed for photoelectrons emitted by the unpolarized (or circularly polarized) X-ray radiation. In the theoretical model used, different approximations for the photoemission cross section were used: the cross sections derived within the dipole approximation or the cross sections corrected for the nondipolar effects. It turned out that the photoelectron signal intensity can be considerably affected in the high energy range by the neglect of the first order correction. The percentage deviations may reach 40%. On the other hand, the influence of the second order correction is less pronounced; the difference between both corrections is below 6%. On the other hand, the parameters needed for quantification of XPS (or HAXPES), the mean escape depth and the effective attenuation length, were found to be practically independent of the photoelectron cross section used in calculations in wide range of the experimental configurations. An attempt has been made to elucidate this unexpected result. A criterion has been proposed that allows prediction of systems and experimental geometries in which the above parameters are insensitive to the photoemission cross sections.