Resonant photoemission study of the electronic structure of CuO and Cu2O

The electronic structures of CuO and Cu2O have been investigated by resonant photoemission at the copper 3p threshold. The experimental data from CuO are compared with the results of a cluster calculation. From this analysis we confirm the dominant d8 character of the states between 8 and 16 eV, and that singlet and triplet final states behave quite differently at the (3p→3d) resonance. It is necessary to specify the multiplet state when calculating the d-d Coulomb interaction in this case since the total energy spread of the d8 multiplets is about 8 eV. The results confirm the charge-transfer nature of the band gap in CuO. The resonance behavior in Cu2O is explained in terms of strong O 2p–Cu 4(sp) hybridization.