ANGLE-RESOLVED INVERSE-PHOTOEMISSION FROM W(001)

Angle-resolved inverse photoelectron spectroscopy (IPS) in the isochromat mode was used to map the unoccupied energy levels of the W(001) surface. Data were collected at room temperature along the GAMMASIGMAMBAR symmetry line of the surface Brillouin zone (SBZ) of the 1 X 1 structure. States observed near 0.5, 3.0 and 4.5 eV above the Fermi level (EF) showed strong sensitivity to surface contamination and were therefore assigned to surface states and/or resonances. These states showed little or no dispersion as expected for states with significant d character. The dispersion of the state near 0.5 eV above E(F) is in good agreement with recent band structure calculations. The implications of our results on the driving force leading to the reconstruction of the W(001) surface are discussed.