Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 43: Adsorption an Oberflächen IV

O 43.6: Vortrag

Freitag, 12. März 2004, 12:30–12:45, H36

Water on Ru(001): Interfacial structure investigated by vibrational spectroscopy — •C. Frischkorn1, D.N. Denzler2, R. Dudek2, S. Wagner2, M. Wolf1, and G. Ertl21Freie Universtät Berlin, Fachbereich Physik, Arnimallee 14–16, 14195 Berlin — 2Fritz–Haber–Institut der MPG, Faradayweg 4–6, 14195 Berlin

Vibrational spectroscopy with sum-frequency generation (SFG) is intrinsically surface/interface sensitive and thus can provide information on the local binding structure in adsorbate layers. In this contribution, we present results on the water structure on ruthenium (D2O/Ru(001)) obtained from SFG spectroscopy. The molecular structure of the first bilayer of this system has been controversially discussed. LEED (low energy electron diffraction) studies revealed an almost coplanar arrangement of the oxygen atoms leading to a vertically compressed bilayer [1]. Recent DFT (density functional theory) calculations found that only a half-dissociated bilayer wets the surface [2] resulting in a coplanar O geometry which consequently explains the LEED results. Our SFG vibrational spectra on D2O/Ru(001) taken at various thicknesses, however, clearly disagree with both structures proposed. Therefore, we suggest a D2O bilayer of intact water molecules whereby every second molecule undergoes a hydrogen-metal bond giving rise to a so-called "hydrogen-down" structure [3].

[1] G. Held, D. Menzel, Surf. Sci. 327, 301 (1995).

[2] P. J. Feibelman, Science 295, 99 (2002).

[3] D. N. Denzler, C. Hess, R. Dudek, S. Wagner, C. Frischkorn, M. Wolf, G. Ertl, Chem. Phys. Lett. 376, 618 (2003).

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