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Abstract

The local structure of ammonia adsorbed on Cu(111) has been determined using N 1s scanned-energy-mode photoelectron diffraction. The molecule is found to occupy an atop bonding site with a Cu−N bond length of 2.09 ± 0.03 Å, but with large amplitude vibrations of the molecule parallel to the surface, consistent with a systematic trend found in our studies of species adsorbed in atop sites. We find no evidence for a significant static offset of the molecule from the atop site (which was found on the lower-symmetry Cu(110) surface), but a small offset of this kind cannot be distinguished from the effects of the large dynamic displacement. As a first test for this photoelectron diffraction technique we have also investigated the effect of including the weakly scattering H atoms in the analysis. This does lead to preferred sites for the H atoms consistent with expectations, but their precision of location is too poor to provide information of chemical significance.