Tilted adsorption of benzene on Pt(110) 1 × 2

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The adsorption of benzene on the reconstructed Pt(110) 1 × 2 surface was studied by temperature-programmed desorption (TPD), low-energy electron diffraction (LEED), angle-resolved UV photoemission (ARUPS) and near-edge X-ray absorption spectroscopy (NEXAFS). At 100 K, benzene is molecularly adsorbed on the Pt(110) 1 × 2 surface. The saturated layer is disordered and corresponds to a coverage of ∼0.28 ML. Annealing to 280 K leads to partial benzene desorption and to the formation of a well-ordered (4 × 2) layer (relative to the unreconstructed surface) with a coverage of 0.25 ML. The missing ( (2n + 1) 4 , 0) adsorbate LEED spots along [11̄0] indicate a glide plane in the adsorbate structure and the existence of two molecules per unit cell. In this layer, benzene adsorbs with the molecular plane tilted by ∼30° in the [001] direction, as determined from ARUPS and NEXAFS. This geometry corresponds to a nearly flat adsorption on the (111) microfacets of the troughs of the reconstructed surface. The molecules have a well-defined azimuthal orientation with a CH bond along the [11̄0] azimuth. For dilute layers ( ϑ = 0.12 ML) and a disordered layer with the same coverage as the ordered layer ( ϑ = 0.25 ML), the molecules are also titled into the troughs, a preferential azimuthal orientation is, however, not observed.