Triple-peak feature of Cu 2p x-ray-photoemission spectrum in copper acetylacetonate

The Cu 2p x-ray-photoemission spectrum (XPS) of copper (II) acetylacetonate Cu(acac)2 is measured. Both the 2p3/2 and 2p1/2 XPS show triple-peak features, which resemble the Ni 2p XPS in NiCl2. By means of a cluster model, however, it is shown that the origin of the triple-peak feature in Cu(acac)2 is quite different from that in Ni dihalides. In Cu(acac)2, the main peak originates from one well-screened final state (2p53d10L), where L denotes a ligand hole, while the two satellite peaks comes from the bonding and antibonding states between the other well-screened state and a poorly screened state (2p53d9). The energy splitting in the 2p53d10L states originates from strong hybridization between O 2p and C 2p orbitals.