The electronic structure and orientation of styrene adsorbed on FeO(111) and Fe3O4(111) - A spectroscopic investigation

The adsorption of styrene on (111)-oriented thin layers of FeO and Fe3O4 ep itaxially grown on Pt(111) single-crystal surfaces has been investigated us ing near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-r ay photoelectron spectroscopy (XPS). High-resolution gas-phase measurements were recorded, and precise ab initio electronic structure calculations wer e performed in order to aid the assignment of the NEXAFS resonances. Wherea s on Fe3O4 (magnetite), styrene forms a chemisorbed monolayer that is stabl e up to room temperature, on FeO (wustite), a significantly more weakly bou nd (physisorbed) species is observed that is stable only for temperatures b elow 200 K. A planar adsorption geometry is observed in the case of styrene on Fe3O4 in the low-coverage regime (Theta < 0.5 ML); for higher coverages on the same surface and on FeO, the average tilt angle between the phenyl plane and the surface plane amounts to about 45 degrees.