AVS 45th International Symposium
    Surface Science Division Monday Sessions
       Session SS2-MoM

Paper SS2-MoM1
An X-ray Absorption Study of Saturated Hydrocarbons Physisorbed on Metal Surfaces

Monday, November 2, 1998, 8:20 am, Room 309

Session: Molecular Adsorbates on Metals
Presenter: C. Wöll, Ruhr-Universität Bochum, Germany
Authors: K. Weiss, Ruhr-Universität Bochum, Germany
C. Wöll, Ruhr-Universität Bochum, Germany
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Monolayers of linear and cyclic saturated hydrocarbons (n-hexane, cyclohexane, n-octane, n-hexatriacontane) physisorbed on several metal surfaces (Cu(111), Au(111), Ru(0001) and Pt(111)) have been investigated by K-edge X-ray absorption spectroscopy (XAS). Whereas the corresponding multilayer data qualitatively resembles the core excitation spectrum observed for the free molecules, a strong quenching of the Rydberg R-resonance at 287.7 eV is observed for molecules in direct contact with the substrate. The intereaction with the metal surface is found to result in the formation of a new, sharp resonance which is assigned to a novel surface-induced Rydberg state. In addition the broad feature observed in the saturated hydrocarbon monolayer XAS-spectra at 285.1 eV is identified as a transition into metal-molecule hybrid orbitals, indicating a significant chemical interaction between saturated hydrocarbon and the metal surface. This C-H-activation is shown to correlate with the well-known soft C-H--stretch modes seen in IR-spectroscopy for many saturated hydrocarbon/metal surface combinations.@footnote 1@ @FootnoteText@ @footnote 1@G. Witte, K. Weiss, P. Jakob, J. Braun, K.L. Kostov, and Ch. Wöll, Phys. Rev. Lett. 80, 121, (1998)