Electronic structure of complex copper systems probed by resonant inelastic X-ray scattering at Cu L3 edge

We have used X-ray absorption (XA) and resonant inelastic X-ray scattering (RIXS) spectroscopies to study a series of copper compounds, namely Cu2O, CuO, Cu(OH)2, CuCl2, Cu2S, CuSO4, malachite (Cu2(CO3)2(OH)2) and atacamite (CuCl2·3Cu(OH)2). Cu 2p XA spectra provide information about oxidation states. Divalent copper gives a single narrow line due to excitations into the empty 3d state, whereas monovalent copper gives a broad band at higher energy due to transitions to 4s states. Chemical shifts of the main line in the Cu2+ XA spectra of different compounds are observed but in some cases they are too small to make a clear distinction between the species. It is shown that RIXS at the Cu 2p edge has a great potential to distinguish between the species due to large differences in spectral shapes for the same energy of the incident photon beam. First evidence for the possibility of detecting chemical composition of copper compounds is presented and discussed in details.