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 ground state 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.