Isochromat inverse photo-emission spectroscopy, at a photon energy of 20eV, was used to map an intrinsic surface state/resonance in the Gamma M direction of the W(001) two-dimensional Brillouin zone. The state was found just above the Fermi level approaching halfway along the Sigma line and disperses upwards to approximately 2eV above the Fermi level towards M. Calculations of the surface electronic structure and the role of the surface states in the reconstruction of the W(001) surface were discussed in the light of the data presented together with existing high-resolution angle-resolved photoemission spectroscopy data.

Unoccupied Surface States of W(001) Studied by Angle-Resolved Ultraviolet Inverse Photoemission. I.R.Collins, A.D.Laine, P.T.Andrews: Journal of Physics - Condensed Matter, 1992, 4[11], 2891-901