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, epsilon F, even if the f level is fairly far below epsilon 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.
 

Physical Review Letters, 50 604-7, 1983.