Evidence for the tetravalence of cerium in CeRu2

Abstract The conventional analysis of XPS core level spectra of Ce Ru 2 yields a pricture of the 4f state which is difficult to reconcile with other results. The validity of this kind of interpretation urgently needs to be re-examined critically. In contrast, Bremsstrahlung isochromat spectroscopy (BIS) measurements on CeRu 2 , reported herein, suggest that Ce is nearly tetravalent 4f 0 configuration) in this compound.