Bulk screening in core level photoemission from Mott-Hubbard and Charge-Transfer systems

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We report bulk-sensitive hard X-ray (hν = 5.95 KeV) core level photoemission spectroscopy (PES) of single crystal V₁.₉₈Cr₀.₀₂O₃ and the high-Tc cuprate Bi₂Sr₂CaCu₂O₈₊δ (Bi2212). V₁.₉₈Cr₀.₀₂O₃ exhibits low binding energy "satellites" to the V 2p "main lines" in the metallic phase, which are suppressed in the antiferromagnetic insulator phase. In contrast, the Cu 2p spectra of Bi2212 do not show temperature dependent features, but a comparison with soft X-ray PES indicates a large increase in the 2p⁵ 3d⁹ "satellites" or 3d⁹ weight in the bulk. Cluster model calculations, including full multiplet structure and a screening channel derived from the coherent band at the Fermi energy, give very satisfactory agreement with experiments.