THE UNOCCUPIED STATES OF A RARE-EARTH-METAL - Y(0001)

Normal incidence inverse photoemission spectra of Y(0001) have been measured in the photon energy range 12-32 eV. In the photon energy range 19-23 eV fluorescence from the radiative decay of a 4p core hole largely obscures the direct transitions. Outside this range a number of features were observed, which vary in intensity but show negligible dispersion with photon energy. Their positions are in good agreement with high density-of-states points along the GAMMA-A direction of published bandstructure calculations. A feature is observed 0.5 (+/- 0.2) eV above the Fermi level, in the gap between the GAMMA-4- and GAMMA-3+ critical points, which may be due to either a surface state or to the high overall density of states at the Fermi level.