Comments on the electronic structure of nickel

We comment on some recent theoretical discussions concerning the electronic structure of nickel and more particularly the position and the weight of the satellite observed in ultraviolet-photoemission spectra (UPS) and x-ray-photoemission spectra (XPS) experiments. We argue that there is no fully satisfactory quantitative theory at the moment for dealing with correlation effects within the d band. The ratio U/W (U is the Coulomb integral, W is the d-band width) is shown to be most probably in the range 0.5-1. The observed narrowing of the d band and Auger spectra are also briefly discussed.