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 coinci des with the Ce 3d-->4f (M(4.5)) absorption edge. Different spectral f eatures, corresponding to 4f(1) and 4f(2) configurations in the final state, exhibit distinct resonance profiles. The relative intensities o f 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 conducti on-band states. At resonance the spectral line shape is unambiguously modified when the temperature is varied across the characteristic Kond o temperature.