To calculate realistic models of objects with Ni in their atmospheres, accurate atomic data for the relevant ionization stages need to be included in model atmosphere calculations. In the context of white dwarf stars, we investigate the effect of changing the Ni IV-VI bound-bound and bound-free atomic data on model atmosphere calculations. Models including photoionization cross-section (PICS) calculated with AUTOSTRUCTURE show significant flux attenuation of up to similar to 80 per cent shortward of 180 angstrom in the extreme ultraviolet (EUV) region compared to a model using hydrogenic PICS. Comparatively, models including a larger set of Ni transitions left the EUV, UV, and optical continua unaffected. We use models calculated with permutations of these atomic data to test for potential changes to measured metal abundances of the hot DA white dwarf G191-B2B. Models including AUTOSTRUCTURE PICS were found to change the abundances of N and O by as much as similar to 22 per cent compared to models using hydrogenic PICS, but heavier species were relatively unaffected. Models including AUTOSTRUCTURE PICS caused the abundances of N/O IV and V to diverge. This is because the increased opacity in the AUTOSTRUCTURE PICS model causes these charge states to form higher in the atmosphere, more so for N/O V. Models using an extended line list caused significant changes to the Ni IV-V abundances. While both PICS and an extended line list cause changes in both synthetic spectra and measured abundances, the biggest changes are caused by using AUTOSTRUCTURE PICS for Ni.

Cheung Ching Ying. / Bibliography: leaf 126 / Thesis (M.Phil.)--Chinese University of Hong Kong

Lam Lik. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 107-112). / Chapter Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- Chemistry of portland cement manufacture --- p.1 / Chapter 1.2. --- Classical methods of cement analysis --- p.7 / Chapter 1.3. --- Application of instrumental methods in cement analysis --- p.12 / Chapter 1.3.1. --- X - ray fluorescence spectrometry --- p.12 / Chapter 1.3.2. --- Atomic absorption spectrometry --- p.16 / Chapter 1.3.3. --- Other instrumental methods --- p.22 / Chapter 1.4. --- Treatment of data --- p.25 / Chapter 1.5. --- Dissolution techniques for AAS analysis --- p.28 / Chapter 1.5.1 --- Hydrofluoric acid decomposition --- p.28 / Chapter 1.5.2 --- Fusion --- p.30 / Chapter 1.6. --- Research objective --- p.34 / Chapter Chapter 2. --- Analysis of Cement and Raw Meal Samples --- p.35 / Chapter 2.1. --- Experimental --- p.36 / Chapter 2.1.1. --- Reagents --- p.35 / Chapter 2.1.2. --- Instrumental --- p.37 / Chapter 2.1.3. --- Procedure --- p.37 / Chapter 2.1.3.1. --- "Sample solutions for the determination of SiO2, A1203, Fe2O3, Ti02, Na20 and K20" --- p.37 / Chapter 2.1.3.2. --- Sample solutions for the determination of CaO and MgO --- p.38 / Chapter 2.1.3.3. --- "Standard solutions for the determination of SiO2, Al2O3， Fe203, TiO2, Na2O and K2O" --- p.33 / Chapter 2.1.3.4. --- Sample solutions for the determination of CaO and MgO --- p.41 / Chapter 2.1.3.5. --- X-ray briquettes --- p.42 / Chapter 2.2. --- Results and discussion --- p.43 / Chapter 2.2.1. --- The proposed fusion system --- p.43 / Chapter 2.2.2. --- Instrumental conditions --- p.47 / Chapter 2.2.3. --- Accuracy --- p.56 / Chapter 2.2.4. --- Interferences studies --- p.61 / Chapter 2.2.5. --- "Calibration graph, detection limits and precision" --- p.69 / Chapter 2.2.6 --- Real sample analysis --- p.80 / Chapter Chapter 3. --- Analysis of Siliceous Materials and Coal --- p.84 / Chapter 3.1. --- Experimental --- p.84 / Chapter 3.1.1. --- Reagents and instruments used --- p.84 / Chapter 3.1.2. --- Procedure --- p.85 / Chapter 3.1.2.1. --- "Sample solutions for the determination of SiO2, A1203, Fe2O3, Ti02, Na20 and K20" --- p.85 / Chapter 3.1.2.2. --- Sample solutions for the determination of CaO and MgO --- p.85 / Chapter 3.1.2.3. --- "Standard solutions for the determination of Si02, Al2O3, Fe2O3,TiO2, Na20 and K20 in siliceous material and coal" --- p.86 / Chapter 3.1.2.4. --- Standard solutions for the determination of CaO and MgO --- p.87 / Chapter 3.1.2.5. --- X - ray briquettes --- p.88 / Chapter 3.2. --- Results and discussion --- p.88 / Chapter 3.2.1. --- Fusion of siliceous materials --- p.88 / Chapter 3.2.2. --- Fusion of coal --- p.93 / Chapter 3.2.3. --- Accuracy and precision --- p.95 / Chapter 3.2.4. --- Real sample analysis --- p.99 / Chapter Chapter 4. --- Conclusion --- p.103 / Chapter 4.1. --- Comparison of XRF and AAS as analytical means in the cement industry --- p.103 / Chapter 4.2. --- The proposed fusion system --- p.105 / References --- p.107

<p>Worldwide there are significant efforts to build networks that can distribute photonic entanglement, first with applications in communication, with a long-term vision of constructing fully connected quantum processing networks (QPN). We have constructed a network of atom-light interfaces, providing a scalable QPN platform by creating connected room-temperature qubit memories using dark-state polaritons (DSPs). Furthermore, we combined ideas from two leading elements of quantum information namely collective enhancement effects of atomic ensembles and Cavity-QED to create a unique network element that can add quantum processing abilities to this network. We built a dual connection node consisting of two moderate finesse Fabry-Perot cavities. The cavities are configured to form a cross-cavity layout and coupled to a cold atomic ensemble. The physical regime of interest is the non-limiting case between (i) low N with high cooperativity and (ii) free-space-high-N ensembles. Lastly, we have explored how to use light-matter interfaces to implement an analog simulator of relativistic quantum particles following Dirac and Jackiw-Rebbi model Hamiltonians. Combining this development with the cross-cavity node provides a pathway towards quantum simulation of more complex phenomena involving interacting many quantum relativistic particles.

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Knowledge of the electric and magnetic elastic form factors of the nucleon is essential for an understanding of nucleon structure. of the form factors, the electric form factor of the neutron has been measured over the smallest range in Q2 and with the lowest precision. Jefferson Lab experiment 02-013 used a novel new polarized 3He target to nearly double the range of momentum transfer in which the neutron form factor has been studied and to measure it with much higher precision. Polarized electrons were scattered off this target, and both the scattered electron and neutron were detected. GEn was measured to be 0.0242 +/- 0.0020(stat) +/- 0.0061(sys) and 0.0247 +/- 0.0029(stat) +/- 0.0031(sys) at Q2 = 1.7 and 2.5 GeV2, respectively.

Solid state deuteron NMR experiments, especially magic angle spinning (MAS) and off-magic angle spinning (OMAS), are developed to explore dynamical systems. A theoretical discussion of interactions relevant for spin-1 nuclei is presented. Practical aspects of MAS/OMAS experiments are described an detail. The dominant quadrupolar coupling interaction in deuteron NMR has been simulated and the effects of multiple-frame molecular motions on MAS/OMAS spectra are taken into account in this calculation. Effects of chemical shift anisotropy are also simulated, and shown to be small under conditions of rapid sample spinning.;Two numerical methods, direct integration and an efficient simulation routine based on Floquet thoery, are discussed. Improvements in computational efficiency of the Floquet method in computing solid stae deuteron MAS/OMAS spectrum makes the quantitative analysis of molecular motion possible: complex multiple frame molecular motions, deuteron quadrupolar interactions and chemical shift anisotropy are now included in a single simulation routine and the effects of the multiple-frame molecular motions can be analyzed by comparing the line shapes of simulations with those of experiments.;The enhanced motional sensitivity of deuteron NMR MAS/OMAS makes it possible to detect temperature-dependent motion rates of urea molecules in octanoic acid/urea inclusion compounds. Temperature-dependent deuteron OMAS line shapes have been recorded and fitted through least-square procedures, to provide rates of rotation about both CN and CO bonds. Activation energies have been calculated for these motions. The power and utility of OMAS is demonstrated by this investigation.;The phenyl ring motions in appropriately labeled L-phenylalanine and N-acetyl-L-phenylalanine methyl ester/cyclodextrin inclusion compound have also been studied through high field deuteron MAS experiments. Phenylalanine MAS spectra with ultra-fast ring-flip motion have been simulated and the range of phenyl ring flip rates is obtained by comparing the simulated and experimental spectra. In the studies of phenylalanine/cyclodextrin inclusion compound, an approach to a physically reasonable diffusion model has also been made by increasing the number of jump sites per unit solid angle included in the calculation. These simulations involve repeated diagonalization of very large matrices and demonstrate the capability of the approach to handle complex dynamical systems.

In recent years, a great deal of progress has been made in understanding the ionization processes that result from the interaction of an intense laser pulse with multielectron atoms. However, due to experimental limitations, the effect of the laser field's spatial dependence on strong-field processes has rarely been investigated. Presented in this work is a theoretical analysis of this spatial dependence including a proposal for an experimentally observable result of the phenomenon. We begin by outlining the elements of the laser field that will vary as a function of position and show their effects on simple free electron trajectories. We then develop a classical, three-dimensional simulation of the entire process of double ionization of helium in an intense laser field using realistic, non-paraxial focal conditions. The existence of an out-of-phase electric field component in the laser propagation direction is determined, which produces an effective longitudinal ellipticity, resulting in a reduction in the double ion yields as a function of position in the laser focus. It is found that under conditions of tight focusing, the effective focal volume for non-sequential double ionization is significantly reduced.

The recent prospect of efficient, reliable, and secure quantum communication relies on the ability to coherently and reversibly map nonclassical states of light onto long-lived atomic states. A promising technique that accomplishes this employs Electromagnetically Induced Transparency (EIT), in which a strong classical control field modifies the optical properties of a weak signal field in such a way that a previously opaque medium becomes transparent to the signal field. The accompanying steep dispersion in the index of refraction allows for pulses of light to be decelerated, then stored as an atomic excitation, and later retrieved as a photonic mode. This dissertation presents the results of investigations into methods for optimizing the memory efficiency of this process in an ensemble of hot Rb atoms. We have experimentally demonstrated the effectiveness of two protocols for yielding the best memory efficiency possible at a given atomic density. Improving memory efficiency requires operation at higher optical depths, where undesired effects such as four-wave mixing (FWM) become enhanced and can spontaneously produce a new optical mode (Stokes field). We present the results of experimental and theoretical investigations of the FWM-EIT interaction under continuous-wave (cw), slow light, and stored light conditions. In particular, we provide evidence that indicates that while a Stokes field is generated upon retrieval of the signal field, any information originally encoded in a seeded Stokes field is not independently preserved during the storage process. We present a simple model that describes the propagation dynamics and provides an intuitive description of the EIT-FWM process.