Electronic structure of CO adsorbed on a Cu(111) surface analyzed with molecular cluster models

• Using the self-consistent Hartree-Fock-Slater model we have calculated the electronic structure for various Cux(CO)y clusters symbolizing not only CO bound to "on-top" and "bridge" sites but also some lateral CO-CO interaction on a Cu(111) surface. By comparison with experimental photoemission data we are able to reproduce the observed energies of the occupied CO 4σ, 1π, and 5σ orbitals as well as the partly occupied 2π orbital. In our model we assume CO to be adsorbed on "top" sites for coverages less than ⊖=0.33 [(sqrt[3]×sqrt[3])R30°] and on both top and bridge sites for ⊖>0.33. The experimentally observed peak of intensity at the Fermi edge which increases with coverage above 0.33 is in our model explained by the occupation of CO orbitals of the b1 and b2 symmetry types, i.e., "π" orbitals, degenerate for top positions (C3v), split by the change to bridge positions (C2v). Our results further indicate that the broadened 5σ-1π intensity peak at high coverages is a result of CO bound to top and bridge sites.

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NATURVETENSKAP  -- Fysik -- Annan fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Other Physics Topics (hsv//eng)

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