RELATIVE IMPORTANCE OF RECENT IMPROVEMENTS IN THE MODELING OF SUBSTRATE X-RAY PHOTOELECTRON DIFFRACTION - NI 2P3-2 EMISSION FROM NI(001)

In an attempt to assess the relative importance of recent improvements in the theoretical description of X-ray photoelectron diffraction (XPD) data we consider an extensive set of Ni 2p3/2 azimuthal measurements from a clean Ni(001) surface, taken at a very high angular resolution of approximately ±1.0°. In particular, we discuss the sensitivity of the theory-experiment agreement to the variation of the following parameters: Cluster size, electron inelastic attenuation length, substrate inner potential, photon polarization, angular broadening due to the finite acceptance of the electron analyzer, and the absolute accuracy in the experimental emission directions relative to the crystal axes. It is then demonstrated how different levels of scattering cluster theory, including single scattering (SS) of plane p-waves, SS of spherical p-waves, SS of spherical waves with proper angular momentum final states, and finally multiple scattering (MS) of spherical waves, affect the calculated XPD curves. Experiment and theory are compared by means of R-factors, and we are thus able to assess the reliability of structural information that one can expect at different levels of theory, thereby minimizing computational complexity. © 1990 IOP Publishing Ltd.