HIGH-ENERGY CE-3D PHOTOEMISSION - BULK PROPERTIES OF CEM2 (M = FE,CO,NI) AND CE7NI3

We study the photon energy dependence of Ce-3d photoemission in CeM2 c ompounds (M = Fe, Co, Ni) and in Ce7Ni3 with measurements taken with s ynchrotron radiation in the photon energy range 1050-3850 eV. The resu lts show a drastic increase of the bulk sensitivity at the higher ener gies due to the increase of the photoelectron escape depth. The spectr a at 3850 eV are largely dominated by the bulk contribution, which is typically 85% of the total intensity in the CeM2 compounds. The result s allow us to obtain the bulk contribution to the spectra in CeM, with a procedure presented here and giving the fractional weights of the b ulk f(0), f(1), and f(2) configurations. In the CeM2 compounds a corre lation is found between these spectral weights and the crystallographi c data showing that the hybridization is nonmonotonic versus the atomi c number of the transition metal. We discuss the results both in conne ction with an impurity model and with the available calculations in an itinerant model. Moreover, the results suggest that the bulk hybridiz ation in CeM2 systems with heavy transition metals has been probably u nderestimated up to now.