Matrix element effects in angle-resolved valence band photoemission with polarized light from the Ni(111) surface

Photoemission intensities from angle-resolved photoelectron spectroscopy with polarized synchrotron radiation were measured and calculated for a magnetization averaged Ni(111) single-crystal surface. Concentrating on the large variations of intensity in dependence on the experimental geometry and parameters, we discuss the exchange-split sp bands crossing E-F and identify strong matrix-element effects that are not dependent on selection rules involving parity. Comparison of experimental intensities with ab initio photoemission calculations provides a firm basis for disentangling symmetry from intrinsic effects due to the initial state. The calculated spectra provide a direct connection between ground-state properties (given by the spectral function) and the experimental intensities.