XAS and XPS Study of Electronic Structure of the Tivalent Cuprate the La2Li0.5Cu0.5O4-d.

Well-characterized stoichiometric La2Li0.5Cu0.5O4-delta (delta almost-equal-to 0.04) has been studied using high resolution CuL3- and OK-edges absorption (XAS) and Cu 2p3/2 X-ray photoelectron spectroscopy (XPS) techniques. The system is found not to have any Cu 3d8 configuration in its ground state but instead reveals a high density of the holes created by doping of monovalent lithium for the divalent copper in the oxygen 2p levels resulting in a 3d9L copper configuration by charge transfer. The formal valence of copper in it is found to be as high as almost-equal-to 2.84 in agreement with chemical analysis. The empirical correlation between the shift of the main XPS line (3d10L) and intensity ratio of the satellite (3d9) to the main line is examined and, also, a new correlation between the energy spread of the XPS satellite and the energy separation of the CuL3 absorption lines due to transitions from (3d9) and (3d9L) states is suggested