Resonant X-ray fluorescence spectroscopy of correlated systems: A probe of charge-transfer excitations

X-ray fluorescence spectroscopy with monochromatic photon excitation is presented as a tool for studies of charge-transfer excitations in correlated systems, using CeO2 and UO3 as examples. Ce 4f --> 3d and U 5f --> 3d x-ray fluorescence, with excitation near the 3d thresholds, probes states as eigenvalues for the groundstate Hamiltonian from the Anderson impurity model. Sweeping the excitation energy across 3d absorption edges enhances contributions of different electronic configurations to fluorescence so that observed resonances indicate the charge-transfer origin of the absorption satellites.