HYBRIDIZATION EFFECTS IN UNOCCUPIED 4F STATES OF CE COMPOUNDS

An energy shift of the f(2) feature is detected between inverse photoe mission surface and bulk f Line shapes in Ce compounds. A comparison w ith analogous Lu compounds shows a systematic enhancement of the 4f su rface shift in the case of Ce (up to 0.3 eV). This effect is interpret ed as an extra ''hybridization shift'' in good agreement with the resu lts of an Anderson impurity Hamiltonian calculation. These findings sh ow that the on-site f-f correlation energy does not increase at the su rface indicating unchanged screening dynamics despite the reduced near est-neighbors coordination.