Dispersion of a single $4f$ impurity state in photoemission spectra of   Yb/W(110)
  Angle-resolved photoemission spectra of a monolayer of Yb on W(110) reveal energy splittings and dispersion of the Yb 4f states that are obviously due to their hybridization with W-derived valence bands. These effects occur at well defined points of the surface Brillouin zone although a smearing over reciprocal space is expected from the structural incoherence of the Yb and W lattices. We conclude therefore that dispersion is not related to the periodic arrangement of the $4f$ states but reflects the k-dependent interaction of a single Yb 4f impurity with W bands. 
Yu. S. Dedkov, D. V. Vyalikh, M. Holder, M. Weser, S. L. Molodtsov, C.   Laubschat, Yu. Kucherenko, and M. Fonin