Resonant soft X-ray emission spectroscopy of V2O3, VO2 and NaV2O5

Resonant soft X-ray emission (RSXE) spectra Of V2O3, VO2 and NaV2O5 were recorded for a series of excitation energies at resonances of the V L- and 0 K-absorption band. The V L- and 0 K-emission in these vanadium oxide bands possess considerable overlap. By resonant excitation we can tune the energy to the absorption thresholds, thereby eliminating this overlap. Hereby we obtain the V 3d and O 2p projected density-of-states of the valence band. Resonant inelastic X-ray scattering (RIXS) is found to be weak in V2O3, which we explain as being due to its metallic character at room temperature. Vanadium dioxide (VO2), semiconducting at room temperature, shows considerable RIXS features only at the O X-emission band. Distinct RIXS structures are visible in the RSXE spectra of the insulator NaV2O5. In the emission spectra excited at the V L-thresholds of this ternary vanadium oxide, dd-excitations of the V d(xy) subband at an energy loss of -1.7 eV are observed. Our observation, that RIXS is stronger for insulators than for metals, should be taken advantage of for studying insulator-to-metal transitions in vanadium compounds in the future.