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The Itrax core scanner provides rapid, high resolution, non-destructive sediment core analysis using x-ray fluorescence (XRF) spectrometry and x-radiography. The effect of varying instrument settings are explored. Effects of sample properties on XRF data are tested and the uncertainty in XRF data is considered. Existing methods of quantifying XRF data are evaluated. Comparisons are made with other XRF micro-scanners. Finally, the x-radiographic capability of the Itrax core scanner is compared to x-ray computed tomography. Itrax XRF data is generally optimised by use of a 30kV x-ray tube voltage. Current should be set as high as possible without generation of sum peaks (30mA is often a good value). A chromium anode tube is suitable for use with most samples. Water content has a diluting effect on detected peak areas, but it is shown that the effect can be corrected, removing an obstacle to quantification of Itrax data. Water content can be determined non-destructively from the ratio of incoherent to coherent scatter of characteristic radiation from the x-ray tube anode. Surface slope can change recorded peak areas, but a simple model is developed to correct for this effect. Surface roughness increases variability in data and, if the scale of roughness is similar to the beam size, elemental peak areas may be reduced. The presence of a mixture of grain sizes greatly reduces peak areas for elements in the larger grains. The uncertainty in Itrax data is found to be higher than suggested by the conventional estimate that uncertainty is equal to the square root of the peak area. This information is vital for researchers to decide what significance they should attach to variations in Itrax elemental profiles. Quantification methods for core scanner XRF data are compared and an approach using log-ratio transformations determined to be the best. Additionally, an improved entirely non-destructive, quantification approach is presented in which explicit corrections are made for the diluting effect of water (water content may determined from the ratio of incoherent and coherent scatter of the tube anode characteristic radiation) . Compared to similar instruments, the Itrax core scanner is more tolerant of surface imperfections. Its x-radiographic scanning helps to determine the significance and extent of features revealed in XRF data. Itrax x-radiography provides no match for the level of detail that can be obtained using x-ray computed tomography and is not readily quantified. It does however provide information on features below the sample surface and, in masking small variations, can make the main core features more apparent. Users of the Itrax core scanner are provided with quantification of known effects (water content, surface slope; x-ray tube, current and voltage) and are alerted to issues that were not previously widely known (mixing of grain sizes, size of uncertainty in data). The areas of effective use and limitations of the Itrax core scanner are set out and recommendations made for optimising results. An optimal quantification method is identified. Many of the conclusions may have relevance to other XRF core scanners.

The generation and interaction dynamics of hot electrons from sub-ps and 10 17 - 10 20W/cm lasers with various thickness of Ti foils, were studied through X-ray spectroscopy in three experiments. The two experiments were carried out with the TARANIS laser at Queen's University Belfast with a second harmonic beam (527mm) and with the fundamental beam (1053mm) in the intensity regime 10 17 - 10 18W/cm. We have observed the Ti K-shell radiation yield correlation with the laser intensity and energy absorption efficiency, and thus confirmed the population and temperature of hot electrons generated as a result of the absorbed energy and laser intensity.

The negligible volatility of ionic liquids allows them to be studied by applying ultrahigh vacuum (UHV) techniques, i.e. X-ray photoelectron spectroscopy (XPS). Consequently, this Thesis describes the XPS of ionic liquid-based metal catalytic systems. Correlation between the binding energy derived from XPS and reaction performance is extensively discussed and used to design a catalytic system for the Suzuki cross coupling reaction. To allow comparable information for the solute dissolved in ionic liquids to be obtained, pure ionic liquids and ionic liquid mixtures are analysed. Fitting models of C 1 s spectra for different ionic liquid families are presented. Charge correction methods, specifically the influence of anion basicity on charge correction, are discussed in detail. The cation-anion interaction is investigated for different families of ionic liquids with single and mixed anions. The interaction between catalysts and ionic liquids can also be demonstrated by XPS. The formation of palladium-containing ylidene complexes in ionic liquids is confirmed by XPS and ESI-MS. The influence of anion basicity on the measured binding energy of the palladium centre is explored. The binding energies of Pd 3d for a range of solutions are plotted against several established metrics, i.e. proton affinity, interaction energy and hydrogen bond acceptor ability (P), and are used to reflect the reaction rates for a model Suzuki reaction. After a proper understanding of the correlation between the binding energy of a metal centre and the reaction rate, a palladium-based catalytic system may be optimised for the Suzuki reaction. The reaction rates observed in ionic liquids with differing basicity anions are monitored and correlated back to the binding energy. XPS is also applied to investigate the interaction of catalysts with ligands in ionic liquid-based rhodium systems. The formation of different rhodium ligand-containing complexes is detected by XPS. The influence of anion basicity on the formation of different rhodium-containing complex is discussed. The measured binding energy of the rhodium centre is correlated to the reaction selectivity in the hydroformylation reaction.

Soft X-ray near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy of liquids, an emerging synchrotron radiation technique, has been applied to characterise the local environment of imidazole in aqueous solution to elucidate the structural nature of the well known self-association effects in this system. Atomic core level spectroscopies such as NEXAFS are extremely sensitive to short range structure, including bond lengths and angles as well as coordination numbers, in condensed matter and in molecular systems.N K-edge NEXAFS data were successfully acquired for aqueous imidazole solutions were studied from low concentrations (10−2 mol L−1) to saturation (> 8 mol L−1). Previous UV/Vis studies had established that imidazole undergoes significant self-association already at concentration well below 1 mol L−1 while energy-dispersive X-ray diffraction studies indicated the formation of water mediated hydrogen-bonded self-associated structures of imidazole.NEXAFS revealed that in the concentration range from 0.50 (~100 H2O molecules per imidazole molecule) to the saturation concentration of 8.20 mol L−1 (~7 H2O molecules per imidazole molecule) no significant variation in the local coordination around imidazole molecules takes place. It appears that progressive self-association at higher concentration is not associated with local structural changes.Using ab initio calculations of N K-edge spectra for complex structure models that explicitly included the evaluation of imidazole gas phase data, the imidazole crystal structure as well as imidazole-imidazole and imidazole-solvent interactions in solution, it was possible to relate the observed imidazole spectra to structure models. Systematic calculations evaluating gas phase monomers and oligomers of pure imidazole, the solid state of imidazole, stacked self-associated imidazole clusters in solution, chained structures of self-associated clusters in solution, and explicitly including the water solvation shell were carried out. Comparative measurements in with chloroform solutions shed some light on the nature of the self-associates present at the lower concentrations investigated in this work.Examining also synergistic interactions between imidazole and water the view was obtained that increasing the concentration of imidazole solutions leads to the assembly of self-associated clusters of hydrated imidazole monomers, which are held together by secondary interactions that are weaker than the hydrogen bonding in the hydrate shell. This result demonstrates the suitability of soft X-ray spectroscopy measurements for the investigation of local structure in solutions of molecular organic solutes.

Un-doped, Er3+ doped (TiO2:Er3+) as well as Er3+/Yb3+ co-doped (TiO2:Er3+/Yb3+) nanocrystals with different concentrations of RE3+ (Er3+, Yb3+) were successfully synthesized using the sol-gel method. The powder X-ray diffraction (XRD) spectra revealed that all undoped and doped samples remained in anatase after annealing at 400°C. The presence of RE3+ ions in the TiO2 host lattice was confirmed by conducting elemental mapping on the samples using Scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDX), which was in agreement with X-ray photoelectron spectroscopy (XPS) results. Transmission electron microscope (TEM) images approximated particle sizes of the samples to be between 1.5 – 3.5 nm in diameter and this compares well with XRD analyses. Phonon quantification in TiO2 was achieved using Fourier transform infrared (FT-IR) spectroscopy. Optical bandgap from Ultraviolet/Visible/Near-Infrared was extrapolated from Kubelka-Munk relation and the narrowing of the bandgap for the doped samples as compared to the undoped sample was observed. The photoluminescence PL study of the samples revealed two emission peaks attributed to direct band-gap and defect-related emissions. A laser beam with 980 nm wavelength was used to irradiate the samples, and the displayed emission lines of the TiO2: Er3+ in the visible region of the electromagnetic spectrum confirmed up-conversion luminescence. Enhancement of up-conversion luminescence intensity due to Yb3+ co-doping was observed, indicating an efficient energy transfer process from the sensitizer Yb3+ to the activator Er3+. / Physics / M. Sc. (Physics)