Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 25: Metal substrates: Adsorption of organic / bio molecules III
O 25.6: Vortrag
Dienstag, 23. März 2010, 11:45–12:00, H36
The local structure of the methoxy reaction intermediate on Cu(110): a scanned-energy mode photoelectron diffraction study — •Dagmar Kreikemeyer Lorenzo1, Werner Unterberger1, David Duncan2, Tsenolo Lerotholi2, Matt Bradley2, Jim Robinson2, and David Philipp Woodruff1 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin — 2University of Warwick, Great Britain
Scanned-energy mode photoelectron diffraction (PhD) is a well-established method to determine quantitatively the local structure of adsorbates at surfaces. We apply this method to study the adsorption on a copper surface, Cu{110}, of the methoxy species, an intermediate in the catalytic decomposition of methanol. Previous STM [1] and XPD [2] studies have concluded that methoxy bonds to Cu {110} through the oxygen atom on a three-fold coordinated site. However, our O1s PhD spectra show the strongest modulation at 30° and 40° polar emission angles in the azimuth, consistent only with a short bridge adsorption site. More quantitative analysis, as well as a parallel DFT study, identifies the structure as involving two distinct short-bridge adsorption sites, one on Cu adatoms, with slightly different bond-lengths to the copper atoms below. The results indicate a tilt of the O-C axes of 37° in the azimuth, with the carbon atoms pointing in opposite directions at alternate adsorption site. This tilt is consistent with the XPD results, and creates a zig-zag structure that accounts for the STM images [1].[1] F.M. Leibsle et al., Surf. Sci. 318 (1994)46[2] E. Holub-Krappe et al., Surf. Sci. 173 (1986)176