Resonant inverse photoemission in cerium-based materials

The Ce 4f part of the electron addition spectra of cerium compounds is selectively and resonantly enhanced when the excitation energy coincides with the Ce 3d-->4f (M(4.5)) absorption edge. Different spectral features, corresponding to 4f(1) and 4f(2) configurations in the final state, exhibit distinct resonance profiles. The relative intensities of the f(1) and f(2) resonances may vary by as much as a factor of 50, according to the strength of the hybridization between 4f and conduction-band states. At resonance the spectral line shape is unambiguously modified when the temperature is varied across the characteristic Kondo temperature.