Surface state and surface resonance at the center of the surface Brillouin zone of Cu{001}

Angle-resolved photoemission experiments on Cu{001} reveal a peak at 5 eV and another at 2.2 eV below the Fermi level which are, respectively, a surface state and a surface resonance at the center of the surface Brillouin zone, . The intensities of both peaks relative to the bulk are functions of photon energy and exhibit maxima for final-state momentum values as predicted by the theory of Louie et al. The intensities of both peaks are very sensitive to oxygen contamination of the surface, and their energy positions and dispersions are in good agreement with theoretical predictions. Changes in the polarization of the exciting radiation show that the two states have 1- and 5-like symmetry, respectively, suggesting that they originate from the s-d-hybridized 1 band at the bottom of the Cu d band, and from the 5 band, respectively.