Final-state effects in inverse photoemission from heavy-fermion compounds

It is shown that the anomalously broad resonances observed in inverse photoemission [bremsstrahlung isochromat spectroscopy (BIS)] from uranium-based heavy-fermion systems can be understood in terms of dynamic relaxation effects. The transient, nonadiabatic component of the conduction-electron response to BIS-promoted charge gives rise to final-state processes which show up as significant broadening and shifting of the spectra. Calculations based on the Anderson model give spectra which qualitatively agree with the measured ones.