Resonant soft x-ray emission spectroscopy of NiO across the Ni L-2,L-3 thresholds

We study the electronic structure of NiO using resonant soft X-ray emission spectroscopy across the Ni L-2.3 thresholds. We observe inelastic (Raman) features within 10eV of the elastic peak energy. At the L-3 resonance, the features within 4eV are enhanced and can be directly assigned to the d-d mu ltiplets of NiO, in correspondence to features observed in optical absorpti on spectra. Resonance enhancements of the triplet and singlet states resolv ed in energy confirm a spin-flip transition. Charge-transfer (CT) excitatio ns are also clearly identified by resonance enhancement at photon energies corresponding to the satellites observed in the Ni L-2,L-3 X-ray absorption spectra.