MVV super Coster-Kronig spectra of nickel near the excitation threshold

The MVV super Coster-Kronig (sCK) spectra of metallic Ni have been measured near the 3p excitation threshold by varying excitation photon energy. The results have been interpreted on the basis of the Cini-Sawatzky theory. The measured sCK band has composite structure with features at electron kinetic energy of 49.8, 56.3, 59.5, and 60.5 eV. If we interpret the band at 49.8 eV to be the split-off quasi-atomic band, we can estimate the effective intra-atomic Coulomb energy at a large value of 8 eV. The spectral shape of the MVV sCK band measured by excitation with vacuum ultraviolet light does not coincide with that obtained by the Mg K α excitation or with that of the L3VV Coster-Kronig band. The shape of the MVV sCK spectrum changes as excitation energy changes. The excitation-energy range in which such spectral change occurs extends from the 3p threshold to 10 eV above it. As the kinetic energy for the MVV sCK band starts to overlap that of the two-hole-bound-state band, the MVV sCK band changes its shape considerably and the two spectra become inseparable. In this excitation-energy region, the spectator electron excited optically forms a virtual bound state with the two 3d holes. The location of the apparent two-hole-bound-state band shifts toward high binding energy on the 3p-3d resonance. This can be interpreted as a kind of final state interaction. The suggested intermediate and final states of the single-step transition are consistent with the constant-initial-state spectra and total photoyield spectrum. The roles of the screening by conduction electrons and the sd hybridization are emphasized