Angular distribution of photoelectrons emitted from noncrystalline solids

Monte Carlo simulations have been performed for studies of the influence of surface excitations on the angular distributions of photoelectron peak intensities. An extended Drude dielectric function, which allows the characteristic oscillator strength, damping constant, and critical-point energy for each subband of valence electrons, is employed to evaluate the position-dependent inelastic mean free paths of photoelectrons emitted from a solid surface. Elastic-scattering cross sections are calculated using phase-shift analysis and the finite difference method for a solid atom with the Hartree-Fack-Wigner-Seitz potential in the Dirac equation. Results of Monte Carlo simulations on the angular distribution of the four electron lines from gold, 4f(7/2), 4d(5/2), 4p(3/2), and 4s are presented. Our calculations reveal that surface effects leads to a reduction of the intensities at small detection angles and a sharp decrease at large angles since the surface excitation is most probable for glancing electrons. However, the difference between the results obtained with and without surface effects may nearly disappear for the ratio of two different photoelectron intensities at small escape angles. Nevertheless, the calculated results taking into account surface effects are in better agreement with the experimental data.