Derivation of the density of unoccupied states in polycrystalline ferromagnetic Fe, Co, and Ni from highly resolved appearance potential spectra

By means of a deconvolution technique, which preserves energy resolution and provides stable results, the densities of unoccupied states in polycrystalline ferromagnetic Fe, Co, and Ni have been derived from highly resolved soft x‐ray appearance potential spectra of the respective 2p3/2 core levels. The maximum of the empty d states is found at 0.23 eV for Ni, 0.55 eV for Co, and 0.92 eV for Fe with energies relative to the Fermi level and errors within ±0.1 eV. Although APS essentially probes a localized DOS, there is good agreement with single‐particle band structure calculations for Ni and probably for Co, too. The higher lying 4s states exhibit a bandlike character in the APS derived DOS. Their energetic position can be reconciled with results from photoemission within the equal core approximation. Deviations from theory in the APS derived DOS for the empty d states in Fe can be explained by invoking either a surface effect or an orbital symmetry dependent final state effect. The exchange splitting be...