Structural studies of formate and methoxy groups on the Cu(100) surface using NEXAFS and SEXAFS |
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Authors: | Duane A. Outka R.J. Madix Joachim Stöhr |
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Affiliation: | 1. Departments of Chemical Engineering and Chemistry, Stanford University, Stanford, California 94305, USA |
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Abstract: | Local chemisorption geometries of formate (HCO2) and methoxy (CH3O) groups on Cu(100) were examined by means of surface extended (SEXAFS) and near-edge X-ray absorption fine structure (NEXAFS) measurements above the O K edge. At 300 K the oxygen of the formate group are equivalent and asymmetrically located near the four-fold hollow site yielding two CuO distances between 2.31 and 2.45 Å. These distances are at least 0.3 Å longer than typical CuO distances of surface and bulk compounds due to a Cu-C steric interaction. The CO bonds and the OCO angle of the formate are estimated to be and 127 ± 7°, respectively. At 200 K the methoxy group has a CuO distance of and the CO axis is tilted with respect to the surface normal. The exact chemisorption site of the methoxy goup could not be determined, but the atop site is ruled-out. |
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