Photoemission from Ce Compounds: Exact Model Calculation in the Limit of Large Degeneracy

Abstract

A method is presented for calculating the core and valence spectra of a Ce compound in the impurity model at zero temperature. In the sudden limit this method becomes exact for large degeneracy of the $f$ level. In this limit the valence spectrum has an $f$ peak close to the Fermi energy, ${\ensuremath{\epsilon}}_{\mathrm{F}}$, even if the $f$ level is fairly far below ${\ensuremath{\epsilon}}_{\mathrm{F}}$, and usually there is a second $f$ peak at larger binding energy. These results correlate well with recent experiments for many Ce compounds. Both the core and valence spectra provide information about the occupancy of the $f$ level and about its coupling to the conduction band.