Valence excitations observed in resonant soft X-ray emission spectra of K2Ni(CN)4.H2O at the Ni 2p edge

Resonant soft X-ray emission spectra have been measured at the Ni 2p edge of a planar nickel complex K2Ni(CN)4·H2O and interpreted by performing ab initio configuration interaction calculations. This cyano complex shows characteristic metal-to-ligand charge transfer (MLCT) bands in the Ni 2p photoabsorption spectra. Resonant soft X-ray emission via the MLCT intermediate states can be interpreted as valence MLCT excitations within a one-electron picture. On the other hand, resonant soft X-ray emission via the intra-atomic Ni 2p–3d intermediate state corresponding to the white line excitation shows significant electron correlation effects.