The authors studied the chemical shift and the Cu 2p core level photoemission spectra of Cu2O, CuO and NaCuO2, where Cu is formally mono-, di- and trivalent, respectively. They performed ab initio band structure calculations and found that the variation in the net charge of the Cu atom is small. The smallest net positive charge is found in the trivalent compound. Nevertheless, the calculated chemical shift follows chemical intuition. They provide an explanation using a counting argument. The 2p core level line shapes show large variations between the different compounds. For CuO, the leading peak has a large broadening and the largest satellite has a large weight, while for Cu2O the main peak is narrow and there is only little weight in the satellite region. NaCuO2 is in these respects intermediate between CuO and Cu2O. These properties are explained using an Anderson impurity model, with parameters obtained from the ab initio calculations. Most of the properties can be related to the formal valence of Cu, by using the same counting argument.
 

in: Synchrotron Radiation and Dynamic Phenomena, ed.: A. Beswick. New York: AIP (1992), 550-564, (= Conference Proceedings No. 258: Grenoble 1991).