Unoccupied surface electronic structure of Gd(0001)

The unoccupied surface electronic structure of Gd(0001) was investigated with high-resolution inverse-photoemission spectroscopy. An empty surface state near EF is observed at Γ̄. Two other surface-sensitive features are also revealed at 1.2 and 3.1 eV above the Fermi level. Hydrogen adsorption on Gd surfaces was used to distinguish the surface-sensitive features from the bulk features. The unoccupied bulk-band critical points are determined to be Γ3+ at 1.9 eV and A1 at 0.8 eV. © 1994 The American Physical Society.