Wave-vector conservation upon hybridization of 4f and valence-band states observed in photoemission spectra of a Ce monolayer on W(110)

Angle-resolved resonant photoemission data for a hexagonally ordered monolayer of Ce on W(110) are presented. The spectra reveal a splitting of the 4f(0) ionization peak around a point in k space where a degeneracy with a valence-band state is expected. The phenomenon is described within a simple approach to the periodic Anderson model. It is found that the Ce 4f state forms a band and hybridization predominantly occurs between the 4f and the valence-band states at the same wave vector.