CRYSTAL FIELDS, LINEWIDTHS AND TEMPERATURE-DEPENDENCE IN THE PHOTOELECTRON-SPECTRA OF HEAVY FERMION CE AND YB COMPOUNDS

We report high-resolution photoemission results for the 4f levels in YbCu2Si2 and CeSi2. The data are compared to the predictions of the Anderson impurity model for valence band photoemission. These predicted spectra are obtained both in an approximate fashion by broadening crystal field (CF) states whose parameters are determined from existing neutron scattering data, as well as from a Gunnarson-Schonhammer calculation. Inclusion of crystal fields does not affect our two fundamental conclusions: that there is a natural linewidth in the problem (almost-equal-to 130meV) which is much greater than predicted by the Anderson model, and that the expected temperature dependence of the Kondo resonance is absent. Due to the large natural linewidth, experimental resolution (60-95meV) is not a limiting factor.