Abstract In this thesis, the electronic structure of selected atoms was investigated by means of electron and uorescence spectroscopy. Synchrotron radiation was used to excitate atoms in gas phase. In particular, the photoionization and subsequent Auger decay processes in metal vapours were studied as well as the resonant Auger decay in rare gases. The experimental results were analyzed together with theoretical predictions obtained utilizing the multiconfiguration Dirac-Fock method.

This Licentiate thesis presents research accomplished at theSection of Atomic and Molecular Physics at the Royal Instituteof Technology in Stockholm using photon induced fluorescencespectroscopy (PIFS) during the last two years. The main results presented are summarized: - Neutral photodissociation in CO was observed aftersynchrotron photon excitation in the range 19-26 eV bycollecting dispersed fluorescence from excited neutral C atoms.Follow-up ab initio calculations point out CO Rydberg seriesconverging to the CO+ C and D states as precursors. - The branching ratio between N2 + (B-X)(v’=1,v’’=2) and (v’=0,v’’=1)transitions in the 20-46 eV energy range reveals strongnon-Franck-Condon effects. Ab initio calculations indicate thatthe autoionization of certain superexcited states areresponsible for some of the structures present in the branchingratio curve, confirming the important role of non-Rydbergdoubly excited resonant states (NRDERS) in de-excitationprocesses above the ionization potential. - Photon induced neutral dissociation processes in NO arereported. Neither Rydberg series nor other molecular states inNO known so far can account for the collected data. From abinitio calculations more information regarding the NO precursorstates and the mechanism behind the observed neutraldissociation were obtained. - The details of a new experimental set-up for gas phasefluorescence measurements using synchrotron radiation aredescribed. It is able to perform simultaneous measurements ofdispersed and total fluorescence in the visible range. Thefirst results obtained with this set-up are presented,concerning fluorescence after excitation of the N2 molecules inthe N 1s edge. These four studies conform the set of papers enclosed in theLicentiate thesis. Finally a pre-study to further apply PIFS to speciespreviously excited by microwave discharge is included as futureplans. / NR 20140805

The X-ray optics of synchrotron radiation beamlines are considered in this paper. The characteristics of synchrotron radiation which make it the premier source of light for studies in many regions of the electromagnetic spectrum are given. A chapter is devoted to the collimating, focusing and monochromating optics of two X-ray diffraction beamlines at the National Synchrotron Light Source. The beamlines are operated by the Naval Research Laboratory (NRL) and the Oak Ridge National Lab (ORNL). The major optical components of these beamlines are reviewed in regards to their function and their flexibility. A detailed analysis is performed on the NRL X-ray collimating mirror. The mirror is treated as an elastically bent beam. Deflection and slope error equations are developed which relate the shape of the bent mirror to its ideal surface. Visible light diffraction patterns collected from the mirror helped to establish operating conditions which provide good collimation. When the observed patterns are wed to the theoretical calculations, estimates of the average figure error are made. Finally, the effect of a highly collimated synchrotron beam on the reproducibility of the integrated intensities from polycrystalline materials is considered. The calculations show that except for the most fine grained materials, representative intensity measurements can only be made when the sample is permitted to move. / M.S.

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

No description available.

Precessional dynamics are exploited in the operation of high frequency magnetic devices such as magnetic disk drives, non reciprocal microwave devices and spin transfer oscillators. The trajectory of the precession and its damping are of crucial importance. This thesis presents the characterisation of a variety of magnetic thin film structures performed with a range of phase sensitive techniques. It is possible to obtain new insight by utilising the chemical and site specificity of X-ray Magnetic Circular Dichroism (XMCD) to isolate the precession in different chemical species or at distinct sites in the crystal structure of a chosen material. X-ray Ferromagnetic Resonance (XFMR) combines XMCD and Ferromagnetic Resonance (FMR) phenomena in a technique capable of measuring the FMR response of an alloy or multilayer with both chemical and site specificity. To complement the XFMR technique a low temperature Time-Resolved Magneto Optical Kerr Effect (TR-MOKE) setup has been developed. This allowed for the characterisation of samples at temperatures in the range 4 K to room temperature. A frequency swept Vector Network Analyser FMR (VNA-FMR) setup was developed to allow for a fast method for determining the resonance condition and damping of a range of ferromagnetic thin film samples. In addition a TR-X-ray Photoemission Electron Microscopy (TR-XPEEM) setup has been established which allows images to be obtained with magnetic contrast. The combination of the above techniques has lead to studies on rare earth capped spin valve free layers and the measurement of spin pumping in industrially relevant spin valves.

by Leung Chu Wah. / Parallel title in Chinese characters. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves 181-182). / Acknowledgements --- p.vi / Abstract --- p.vii / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Evaluation of Far Field by Lai and Char's Method --- p.6 / Chapter 2.1 --- Far Field Expression --- p.6 / Chapter 2.2 --- Radiation Power --- p.12 / Chapter 2.3 --- Gaussian Curvature and Point of Stationary Phase of Cylindrically Symmetry DWS --- p.16 / Figures for Chapter2 --- p.19 / Chapter 3. --- Synchrotron Radiation in Vacuum Using Lai and Char's Method --- p.20 / Chapter 3.1 --- The Far Field --- p.20 / Chapter 3.2 --- Current Density for a Gyrating Charge --- p.22 / Chapter 3.3 --- Radiation Power --- p.25 / Chapter 3.4 --- Some Angular Properties of Synchrotron Radiation --- p.29 / Chapter 3.5 --- Total Power Emitted in N-th Harmonic --- p.32 / Chapter 3.6 --- Total Power Emitted in All Harmonics --- p.33 / Figures for Chapter3 --- p.36 / Chapter 4. --- Synchrotron Radiation in a Cold Magnetoplasma --- p.42 / Chapter 4.1 --- DWS for a Cold Magnetoplasma --- p.42 / Chapter 4.2 --- Derivatives of kp and Gaussian Curvature of DWS --- p.45 / Chapter 4.3 --- Group Velocity --- p.46 / Chapter 4.4 --- Current Density --- p.47 / Chapter 4.5 --- Point of Stationary Phase --- p.48 / Chapter 4.6 --- Identification of Different Wave Modes --- p.48 / Chapter 4.7 --- Radiation Power --- p.49 / Chapter 4.8 --- Relation with Vacuum Case --- p.53 / Figures for Chapter4 --- p.56 / Chapter 5. --- Incoherent Radiation from an Assembly of Charges --- p.79 / Chapter 5.1 --- Total Incoherent Energy Flux from N Particles --- p.79 / Chapter 5.2 --- Synchrotron Radiation from Particles with Momentum Distribution --- p.80 / Chapter 5.3 --- Mono-Energetic Particles with Distributed Parallel Momentum --- p.82 / Chapter 5.4 --- "Angular Distribution, Frequency Distribution and Total Radiation Power" --- p.87 / Figures for Chapter5 --- p.88 / Chapter 6. --- Coherent Radiation from an Assembly of Charges --- p.94 / Chapter 6.1 --- Bunching Factor --- p.94 / Chapter 6.2 --- Some Arrangements of Particles --- p.96 / Chapter 6.2.1 --- Charges Distributed Uniformly over an Arc of Angular Width --- p.96 / Chapter 6.2.2 --- Charges Distributed Along a Straight Line --- p.100 / Chapter 6.2.3 --- Charges Distributed Uniformly on a Helical Path --- p.101 / Chapter 6.2.4 --- Charges Distributed Randomly on an Arc --- p.102 / Chapter 6.3 --- Effect of Bunching in a Cold Magnetoplasma --- p.104 / Figures for Chapter6 --- p.105 / Chapter 7. --- Correction to Radiation Power Formula for Degenerate DWS --- p.113 / Chapter 7.1 --- Far Field Expression for Degenerate DWS --- p.113 / Chapter 7.2 --- Radiation Power for Degenerate DWS --- p.115 / Chapter 7.3 --- Alternate Proof for the Extra Factorin (7.2.11) --- p.118 / Chapter 7.4 --- Example of Degenerate DWS - Vacuum --- p.120 / Chapter 8. --- "Ratio of Emitted Power to Received Power, f" --- p.122 / Chapter 8.1 --- Group Velocity in terms of Derivatives of DWS --- p.122 / Chapter 8.2 --- Calculation of Derivatives --- p.124 / Chapter 8.3 --- Expression for f --- p.126 / Chapter 8.4 --- Alternate Form of f --- p.127 / Chapter 8.5 --- Examples of Calculating f Using (8.4.1) --- p.129 / Chapter 8.5.1 --- Isotropic Cold Plasma --- p.129 / Chapter 8.5.2 --- Cold Magnetoplasma --- p.130 / Figures for Chapter8 --- p.132 / Chapter 9. --- Comparison of Far Field by Lai and Chan with that by Others --- p.135 / Chapter 9.1 --- Expressing the Far Field Ratio in terms of Derivatives of DWS and WS --- p.135 / Chapter 9.2 --- Far Field Ratio for an Uniaxial Non-Dispersive Medium --- p.137 / Chapter 9.3 --- Far Field Ratio for an Isotropic Cold Plasma --- p.138 / Chapter 10. --- Minimum Far Field Distance to a Moving Radiating Source in an Anisotropic and Dispersive Medium --- p.140 / Chapter 10.1 --- Sub-Dominant Terms of the Far Field --- p.141 / Chapter 10.2 --- Minimum Far Field Distance --- p.147 / Chapter 10.3 --- Minimum Far Field Distance in an Isotropic Non-Dispersive Medium --- p.152 / Chapter 10.4 --- Minimum Far Field Distance in an Isotropic Dispersive Cold Plasma --- p.156 / Chapter 10.5 --- Minimum Far Field Distance for Alfven Waves in a Cold Magnetoplasma --- p.159 / Chapter 10.6 --- Comparison of Results by Other Authors --- p.162 / Figures for Chapter 10 --- p.165 / Chapter 11. --- Conclusions / Chapter Appendix 1. --- Calculation of the Total Power Emitted in Synchrotron Radiation in Vacuum --- p.170 / Chapter Appendix 2. --- "Derivatives of stix's Parameters and a1,a2 of Equation (4.1.22)-(4.1.23 )" --- p.176 / Chapter Appendix 3. --- Dispersion Relation for Alfven Wavesin a Cold Magnetoplasma --- p.179 / References --- p.181

This thesis is based on studies of multiple ionization of atoms and molecules induced by the absorption of a single photon. For the experimental investigations a time-of-flight magnetic bottle spectrometer has been used to detect the emitted electrons in coincidence. The method of coincidence time-of-flight spectroscopy and the experimental setup used is described. Experimental and theoretical results on molecular double core holes (DCHs) and multiple ionization of atoms are presented. Molecular DCHs are of considerable interest, as their chemical shifts are predicted to be more sensitive than their single core hole counterparts. Using CH4 and NH3 as examples, it is shown that molecules with two vacancies in the innermost shell can be studied using synchrotron light in combination with our coincidence technique. The chemical shifts of S 2p DCHs are investigated for the molecules CS2, H2S and SO2 and the influence of relaxation effects on the shifts are estimated. In the studies of atoms, the main focus is on the processes leading to double and higher degrees of ionization, and the final state populations. In cadmium double photoionization in the photon energy region 40-200 eV occurs mainly by indirect ionization via valence ionized satellite states and through Coster-Kronig decay of inner shell hole states. In valence-valence ionization of krypton by 88 eV photons both direct and indirect ionization processes are found to be important. For the indirect pathways strong final state selectivity in the autoionization decays of the intermediate states is observed. Triple ionization of krypton via intermediate core-valence doubly ionized states is investigated. The intermediate states are observed in the energy region 120-125 eV, and their decay to states of the triply charged ion is mapped. Experimental and theoretical results on the formation of 2p double hole states in argon are presented. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

The development of X-ray Beam Position Monitors (XBPM) used on the Canadian Light Source front ends is described in this thesis, from the design concepts to the practical implementation and commissioning. Surveyed into position to provide a fiducialized point of origin for incoming synchrotron radiation, the primary purpose of the XBPM is to provide a measure of synchrotron beam motion. Currently XBPMs have been installed on three beamlines at the Canadian Light Source, a 2.9 GeV third generation synchrotron radiation source. Two of the XBPMs are comprised of chemical vapour deposition synthetic diamond blades coated with gold and installed on insertion device beamlines, while the third makes use of molybdenum blades for a dipole beamline. By incrementally scanning the blades of the XBPM through the synchrotron beam it is possible to determine the monitors� spatial resolution to beam motion. For the commissioned XBPM a typical spatial resolution of +/- 1 micron of beam motion was achieved; and the thermal power loading capacity has been tested to the 2/5 of maximum value. An independent white beam profiler, comprised of a converter crystal and image acquisition software, was constructed to corroborate the functionality of the XBPM.

Alginate is a popular biomaterial in tissue engineering. When crosslinked with calcium ions (Ca2+), alginate forms a hydrogel which provides necessary mechanical support as a scaffold. The material properties as well as the biological properties of alginate scaffold are of great importance. In this thesis, the aim is to use traditional methods, such as scanning electron microscopy (SEM) and light microscopy, and emerging X-ray imaging techniques, such as micro-computed tomography (micro-CT) and synchrotron radiation (SR) X-ray imaging, to characterize the alginate scaffolds. Firstly, the material properties of freeze-dried alginate scaffolds were evaluated using micro-CT, as it is a non-destructive and non-invasive imaging method, and can provide three-dimensional information. Alginate scaffolds made with different sodium alginate concentrations and frozen to different temperatures were scanned and analyzed in micro-CT. Results indicated that lower freezing temperature and higher sodium alginate concentration lead to smaller pore size and porosity. Secondly, cell culture experiments were carried out to study the biological properties and the interactions of alginate hydrogel with cells. A Schwann cell line was either blended with alginate solution before crosslinking with calcium chloride (CaCl2) or put around alginate gel in the culture dish. Light microscopy of sectioned slices showed that cells surrounding the alginate gel could not grow into the gel, while cells blended with alginate solution before crosslinking could proliferate inside the hydrogel. Cells grown inside a thin slice of alginate gels appeared to be in better condition and were larger in size and also grew in clusters. Thirdly, in order to image soft tissue buried inside alginate gels, such as brain slices, novel imaging methods based on synchrotron radiation (SR) were applied, such as absorption and phase contrast imaging, diffraction-enhanced imaging (DEI) and also combined with computed tomography (CT). Synchrotron-based monochromatic X-ray imaging proved to be good at distinguish objects of similar density, especially biological soft tissue samples, even without any staining material, such as osmium tetroxide (OsO4). These three pieces of research work show the potential in applying the emerging X-ray imaging in soft tissue engineering.