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Instruments / Technical Area	Publication Details	Published
I09-Surface and Interface Structural Analysis	Chemical shielding of H2O and HF encapsulated inside a C60 cage Samuel P. Jarvis , Hongqian Sang , Filipe Junqueira , Oliver Gordon , Joe E. A. Hodgkinson , Alex Saywell , Philipp Rahe , Salvatore Mamone , Simon Taylor , Adam Sweetman , Jeremy Leaf , David A. Duncan , Tien-Lin Lee , Pardeep K. Thakur , Gabriella Hoffman , Richard J. Whitby , Malcolm H. Levitt , Georg Held , Lev Kantorovich , Philip Moriarty , Robert G. Jones Communications Chemistry 4 DOI: 10.1038/s42004-021-00569-0 Diamond Proposal Number(s): [12979, 15022] Open Access Show Abstract ▼ Abstract: Molecular surgery provides the opportunity to study relatively large molecules encapsulated within a fullerene cage. Here we determine the location of an H2O molecule isolated within an adsorbed buckminsterfullerene cage, and compare this to the intrafullerene position of HF. Using normal incidence X-ray standing wave (NIXSW) analysis, coupled with density functional theory and molecular dynamics simulations, we show that both H2O and HF are located at an off-centre position within the fullerene cage, caused by substantial intra-cage electrostatic ﬁelds generated by surface adsorption of the fullerene. The atomistic and electronic structure simulations also reveal signiﬁcant internal rotational motion consistent with the NIXSW data. Despite this substantial intra-cage interaction, we ﬁnd that neither HF or H2O contribute to the endofullerene frontier orbitals, conﬁrming the chemical isolation of the encapsulated molecules. We also show that our experimental NIXSW measurements and theoretical data are best described by a mixed adsorption site model.	Sep 2021
I09-Surface and Interface Structural Analysis	Structural characterisation of molecular conformation and the incorporation of adatoms in an on-surface Ullmann-type reaction Chris J. Judd , Filipe L. Q. Junqueira , Sarah L. Haddow , Neil R. Champness , David A. Duncan , Robert G. Jones , Alex Saywell Communications Chemistry 3 DOI: 10.1038/s42004-020-00402-0 Diamond Proposal Number(s): [18752] Open Access Show Abstract ▼ Abstract: The on-surface synthesis of covalently bonded materials differs from solution-phase synthesis in several respects. The transition from a three-dimensional reaction volume to quasi-two-dimensional confinement, as is the case for on-surface synthesis, has the potential to facilitate alternative reaction pathways to those available in solution. Ullmann-type reactions, where the surface plays a role in the coupling of aryl-halide functionalised species, has been shown to facilitate extended one- and two-dimensional structures. Here we employ a combination of scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and X-ray standing wave (XSW) analysis to perform a chemical and structural characterisation of the Ullmann-type coupling of two iodine functionalised species on a Ag(111) surface held under ultra-high vacuum (UHV) conditions. Our results allow characterisation of molecular conformations and adsorption geometries within an on-surface reaction and provide insight into the incorporation of metal adatoms within the intermediate structures of the reaction.	Nov 2020
I09-Surface and Interface Structural Analysis	Thin film structural analysis using variable-period x-ray standing waves Joshua S. Gibson , Karen L. Syres , Matthew Buckley , Tien-Lin Lee , Pardeep K. Thakur , Robert G. Jones Physical Review B 98, 165402 DOI: 10.1103/PhysRevB.98.165402 Diamond Proposal Number(s): [9118] Show Abstract ▼ Abstract: Variable-period x-ray standing wave (VPXSW) studies have been carried out using 3 keV x rays and photoelectron detection. Two model surfaces have been used, a native SiO2 layer (20 Å thick) on bulk silicon, and a purpose-built multilayer surface comprising a chloroform/water marker layer (12 Å thick) on an ionic liquid spacer layer (211 Å thick) deposited on a SiO2/Si substrate at 90 K. By using photoelectron detection, both chemical and elemental sensitivity were achieved. The surfaces were modeled using dynamic x-ray scattering for x-ray intensity, and attenuation of photoelectrons transmitted through the layers, to produce simulations which accurately reproduced the experimental VPXSW measurements. VPXSW measurements made using the substrate, spacer layer, and marker layer photoelectron signatures produced consistent structural values. This work demonstrates that VPXSW can be used to determine chemically specific layer thicknesses within thick (300 Å) surface structures composed of the light elements B, C, N, O, F, and Cl with an accuracy of 10 to 15 Å, perpendicular to the surface.	Oct 2018
NONE-No attached Diamond beamline	The structure of the Au(111)/methylthiolate interface: New insights fromnear-edge x-ray absorption spectroscopy and x-ray standing waves A. Chaudhuri , M. Odelius , R. Jones , B. Detlefs , T.-l. Lee , D. P. Woodruff Journal Of Chemical Physics 130 (12), 124708 DOI: 10.1063/1.3102095 Show Abstract ▼ Abstract: The local structure of the Au(111)(?3×?3)R30° -methylthiolate surface phase has been investigated by S?K -edge near-edge s-ray absorption fine structure(NEXAFS) both experimentally and theoretically and by experimental normal-incidence x-ray standing waves (NIXSW) at both the C and S atomic sites. NEXAFS shows not only excitation into the intramolecular ? ? S–C resonance but also into a ? ? S–Au orbital perpendicular to the surface, clearly identifying the local S headgroup site as atop a Au atom. Simulations show that it is not possible, however, to distinguish between the two possible adatom reconstruction models; a single thiolate species atop a hollow-site Au adatom or a dithiolate moiety comprising two thiolate species bonded to a bridge-bonded Au adatom. Within this dithiolate moiety a second ? ? S–Au orbital that lies near parallel to the surface has a higher energy that overlaps that of the ? ? S–C resonance. The new NIXSW data show the S–C bond to be tilted by 61° relative to the surface normal, with a preferred azimuthal orientation in ?211? , corresponding to the intermolecular nearest-neighbor directions. This azimuthal orientation is consistent with the thiolate being atop a hollow-site Au adatom, but not consistent with the originally proposed Au-adatom-dithiolate moiety. However, internal conformational changes within this species could, perhaps, render this model also consistent with the experimental data.	Mar 2009

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