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Title: Adsorbate structure determination using energy scanned photoelectron diffraction
Author: Duncan, David A.
ISNI:       0000 0004 2726 0224
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2012
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Energy-scanned photoelectron diffraction was used to determine the local adsorption site of several molecular species on well defined single crystal surfaces. Cytosine and uracil on Cu(110) were found to adsorb with their molecular planes perpendicular to the surface and mostly aligned along the close packed [110] direction. Both molecules were found to adsorb through their constituent oxygen atom(s) and a deprotonated nitrogen atom. The associated Cu-O and Cu-N bond lengths were found to be 1.94 (+0.06/-0.04)Å and 1.94 (+0.07 / -0.03) Å, respectively, for cytosine and 1.96 ± 0.04 / 1.93 ± 0.04 Å and 1.96 ± 0.04 Å, respectively, for uracil. The mono- and bi- tartrate phases of tartaric acid on Cu(110) were found to adsorb via deprotonated carboxylic acid groups with the oxygen atoms in different near-atop sites. The associated Cu-O bond lengths were found to be 1.92 ± 0.08 Å / 1.93 ± 0.06 Å and 1.93 – 1.97 ± 0.06 – 0.09 Å respectively. Glycine on Cu(111) was found to adsorb via both its nitrogen and oxygen constituent atoms, though three competing models were found for the local adsorption site of the oxygen atoms. The nitrogen atom was found to adsorb in a near-atop site with an associated Cu-N bond length of 2.02 ± 0.03 Å. The oxygen adsorption site was found to at least have some near-atop characteristics, with the near-atop site having an associated Cu-O bond length of 2.00 – 2.02 ± 0.04 – 0.07 Å. Reanalysis of the C 1s PhD data of the hydrocarbon remnant from the decomposition of furan on Pd(111) found that the lowest energy model predicted by DFT does not occur, at least in large quantities, on the surface. The most likely structure was found to be CH–C–CH2. On the Ru(0001) surface, dehydrogenation of methanol was not observed in the temperature range around 150 K, with no evidence for the strong modulations in the O 1s PhD spectra predicted for a methoxy species. A reexamination of water adsorption of the rutile TiO2(110) surface found that water does, at least partially, dissociate on the perfect surface as well as at defect sites – in contrast to previously published experimental results. The associated Ti-O bond lengths for the resulting atop and bridging hydroxyl species were found to be 1.85 ± 0.08 Å and 1.94 ±0.07 Å respectively. Finally vanadyl phthalocyanine was found to adsorb upright (with the oxygen atom further from the surface than the vanadium atom) on the Au(111) surface. The V=O bond length was found to be 1.60 ± 0.04 Å.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics