[en] The structure of the Ni(111)(³√x³√)R30 degree sign -Pb surface phase formed by a nominal (1/3) monolayer of Pb has been investigated by medium-energy ion scattering using 100 keV H⁺ ions in three different incidence directions. The results show clearly that the Pb atoms occupy fcc hollow sites at the surface, but also favor a structure in which these are surrounded by Ni atoms to form a surface alloy phase. A surface alloy with a surface stacking fault, as has been found for the (³√x³√) surface alloy phases formed by Sb adsorption on Cu(111) and Ag(111), can be clearly excluded. The preference for a surface alloy structure is consistent with the results of an earlier low-energy ion scattering study, but we find significant differences in the quantitative structural parameters. This structural model also implies a considerable reduction of the effective radius of the Pb atoms relative to their size in bulk Pb, and this is discussed in the context of other quantitative structural studies of substitutional surface alloy phases

[en] 100 keV H⁺ medium-energy ion scattering has been applied to investigate the surface relaxations of the clean rutile TiO₂(110)-(1x1) surface structure. A set of blocking curves in four different incident directions show clear differences between the surface and bulk attributable to surface relaxation. Optimized values of the surface relaxation parameters to give the best fit to the surface structure are generally in quite good agreement with a recent experimental determination of this structure using quantitative low-energy electron diffraction. In particular, both solutions favor an outward relaxation of the bridging O atoms on the surface rather than the strong inward displacement favored by the only previous experimental structure determination based on surface x-ray diffraction

[en] Multimodal chemical tomography is a technique that has to deal with a variety of big (>100 GB) datasets. Here, a novel method for approaching the analysis of such data using a Python-based big data solution is presented. With the development of fourth-generation high-brightness synchrotrons on the horizon, the already large volume of data that will be collected on imaging and mapping beamlines is set to increase by orders of magnitude. As such, an easy and accessible way of dealing with such large datasets as quickly as possible is required in order to be able to address the core scientific problems during the experimental data collection. Savu is an accessible and flexible big data processing framework that is able to deal with both the variety and the volume of data of multimodal and multidimensional scientific datasets output such as those from chemical tomography experiments on the I18 microfocus scanning beamline at Diamond Light Source.

[en] We have constructed a Time-Resolved X-ray Excited Optical Luminescence (TR-XEOL) detection system at the Microfocus Spectroscopy beamline I18 at the Diamond Light Source. Using the synchrotron in ^hybrid bunch mode^, the data collection is triggered by the RF clock, and we are able to record XEOL photons with a time resolution of 6.1 ps during the 230 ns gap between the hybrid bunch and the main train of electron bunches. We can detect photons over the range 180-850 nm using a bespoke optical fibre, with X-ray excitation energies between 2 and 20 keV. We have used the system to study a range of feldspars. The detector is portable and has also been used on beamline B18 to collect Optically Determined X-ray Absorption Spectroscopy (OD-XAS) in QEXAFS mode.