Intersite interactions in CuL-edge XPS, XAS, and XES of doped and undoped Cu compounds

The effect of interaction between different Cu atoms is studied by calculations on clusters with more Cu atoms for various kinds of spectroscopy, using a multiband Hubbard Hamiltonian. It is found that the inclusion of more Cu sites often leads to final states lower in energy than those that would have been found if the calculations were restricted to the Anderson-impurity limit. These effects are studied for both undoped and doped systems. These interactions are not only important for systems involving a core hole but can also be induced by the ${\mathit{U}}_{\mathit{d}\mathit{d}}$ Coulomb interaction. Furthermore, we show that the wide shape of the main line of the Cu 2p XPS spectrum is not incompatible with a narrow 2p XES spectrum within a one-step model.