Surface effects in low energy photoemission of rare earth polycrystalline films_Elettra Proposal Number 20085454

We measured low energy (5-21 eV) photoelectron emission spectra from polycrystalline Yb film grown in situ on a tungsten substrate. We paid particular attention to the region close to the Fermi level, where a prominent peak develops upon reducing the photon energy below about 10 eV, accompanied, at binding energy of about 0.6-0.8 eV, by a large bump. While the origin of this last structure is still puzzling, we attribute the Fermi level peak to the pronounced enhancement, at lower photon energy, of the photo ionization cross section of partly occupied 5d or 6p Yb states.