Bulk screening in core-level photoemission from Mott-Hubbard and charge-transfer systems

We report bulk-sensitive hard x-ray (hν=5.950.3em0exkeV) core-level photoemission spectroscopy (PES) of single crystal V1.98Cr0.02O₃ and the high-Tc cuprate Bi₂Sr₂CaCu₂O_8+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 2p⁵3d⁹ satellites or 3d⁹ weight in the bulk. Cluster model calculations, including a full multiplet structure and a screening channel derived from the coherent band at the Fermi energy, give very satisfactory agreement with the experiments.