Resonant X-ray emission spectra of K₂Ni(CN)₄.H₂O at the Ni K-edge

Resonant X-ray emission spectra were measured at the Ni K-edge for a planar low-spin nickel complex K₂Ni(CN)₄.H₂O. In the Ni K_β emission spectra, a resonant X-ray Raman scattering was observed in the pre-edge region, showing linear energy dispersion of the emitted photon with the incident photon energy. No energy loss features corresponding to the ligand-to-metal charge-transfer (LMCT) was identified. The LMCT feature is characteristic of strongly correlated systems such as NiO; therefore, the LMCT effect proves to be significantly suppressed. This is consistent considering strong covalent character between low-lying π* ligand and metal 3d (occupied) orbitals in low-spin nickel complexes.