Dresden 2014 – scientific programme

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O: Fachverband Oberflächenphysik

O 58: Oxide and Insulator Surfaces II

O 58.5: Talk

Wednesday, April 2, 2014, 17:00–17:15, PHY C 213

LEED-I(V) structure analysis of the physisorption system CO p(2×1)/NaCl(100) — •Jochen Vogt and Birgit Vogt — Chemisches Institut der Uni Magdeburg, Magdeburg, Germany

The system CO/NaCl(100) is one of the model systems of physisorption. Although intensively studied both experimentally and theoretically (see e. g. [1-3]), an experimental structure analysis of its low temperature p(2×1) phase has been missing so far. Using the MCP-LEED technique, we have recorded diffraction peak intensities of the saturated p(2×1) phase as a function of electron energy at a temperature of 21 K. The data were the basis of a full dynamical LEED-I(V) analysis. Our structure model, involving two inequivalent molecules related by the observed glide-plane symmetry, contains only 5 molecular structure parameters, and the rumpling of the substrate surface. According to our results, the carbon end of CO is located 2.58±0.08Å over Na⁺, laterally shifted 0.4±0.1Å towards the neighbor chlorine. The molecular tilt angle is 28±5 degrees with respect to the surface normal, in satisfactory agreement with infrared spectroscopic results [2]. In a structure model with oxygen pointing towards the surface, the Pendry R-factor worsens from 0.22 to 0.25. [1] D. Schmicker, J. P. Toennies, R. Vollmer, H. Weiss, J. Chem. Phys. 95 (1991), 9412 [2] J. Heidberg, E. Kampshoff, M. Suhren, J. Chem. Phys. 95 (1991), 9408 [3] M.-N. Carre et al., Surf. Sci. 347 (1996), 128