Crystal-field states of UO2 probed by directional dependence of nonresonant inelastic x-ray scattering

Nonresonant inelastic x-ray scattering (NIXS) has been performed on single crystals of UO2 to study the directional dependence of higher-order-multipole scattering from the uranium O-4,O-5 edges (90-110 eV). By comparing the experimental results with theoretical calculations the symmetry of the ground state is confirmed directly as the crystal-field (CF) Gamma(5) triplet state within the J = 4 manifold. The results demonstrate that the directional dichroism of the NIXS spectra is sensitive to the CF strength and establish NIXS as a tool for probing CF interactions quantitatively.