Strong anisotropy of resonant inelastic x-ray scattering from charge-transfer excitations in UO3

Resonant x-ray scattering spectra of UO3 were measured at the U M-5 edge using monochromatic photon excitation. Large differences in inelastic scattering profiles were observed between two 90degrees-scattering geometries with the polarization vector of incident synchrotron radiation parallel and perpendicular to the scattering plane, respectively. For the latter case, a similar to9.5 eV energy-loss structure, associated with the O 2p --> U 5f charge-transfer satellite, shows a significant intensity enhancement. The observed resonance behaviour allows an accurate estimation of the energy of this satellite, which is obscured in the other experimental geometry, and indicates the charge-transfer origin of the U M5 absorption structures at the respective excitation energies.