Electron correlations are responsible for many profound phenomena in solid-state physics. A classical example is the 6-eV satellite in the photoelectron spectrum of Ni. Until now the satellite structure has only been investigated at the $L$ shell and more shallow levels. Here we report a high-kinetic-energy photoemission spectroscopy (HIKE) investigation of Ni metal. We present $1s$ and $2p$ photoelectron spectra, obtained using excitation energies up to 12.6 keV. Our investigation demonstrates that the energy position of the satellite relative to the main line is different for the $1s$ and the $2p$ levels. In combination with electronic structure calculations, we show that this energy shift is attributed to unique differences in the core-valence coupling for the $K$ and $L_{2,3}$ shells in $3d$ transition metals, resulting in different screening of the core holes.

• Received 2 December 2008

DOI:https://doi.org/10.1103/PhysRevB.78.233105