Electronic structure of Ni and Pd alloys. II. X-ray photoelectron core-level spectra

Our measurements of the Ni 2p core levels in about 30 alloys show a dependence of the satellite on the chemical environment, which for a given stoichiometry correlates with the electronegativity of the partner. In no case was a complete disappearance of the satellite observed, which is interpreted as evidence for d character in unoccupied states. The general view developed in the preceding paper, that despite the band filling there is no large charge transfer in Ni intermetallic compounds, is confirmed by these observations. The band filling is a result of the mixing of wave functions which are centered on different sites. Studies of the satellite intensity as a function of stoichiometry in alloys with electropositive metals show the satellite to weaken as long as the band is being filled, and then to reach an almost constant intensity at some partner-element concentration. It is not possible to extract similar information from the spectra of Pd compounds because the satellites are weaker and partially obscured by inelastic losses.