In this dissertation I present experimental results obtained on the mercury optical clock project in the research group of Jason Jones at the University of Arizona. The project began in 2008 with the purpose of investigating the feasibility of neutral mercury as an optical clock species. The first series of investigations involved building the essential apparatus and scanning the doppler-broadened 6¹S₀ - 6³P₀ clock transition in ¹⁹⁹Hg. Here I present significant modifications to the cooling and trapping laser, improvements to the spectroscopy laser linewidth, and attempts to measure the 2-photon transition in ¹⁹⁹Hg. After previously demonstrating spectroscopy of the mercury clock transition using an optically-pumped semiconductor laser for the cooling and trapping source (OPSL), we replaced the OPSL with a a fiber-amplified ECLD system. We custom built a fiber amplifier to provide gain at 1015 nm, demonstrating the system can yield up to 5 W of signal power with excellent suppression of the ASE power. We find that the ASE is well suppressed by using a two-stage configuration and short sections of gain fiber. The linewidth of our original spectroscopy laser was over 10 kHz, which is unsuitable to resolve of sub-Doppler features. To enhance the performance of our spectroscopy system, we integrated faster feedback bandwidth using AOMs, and incorporated derivative gain into the system. This resulted in a feedback bandwidth for our spectroscopy laser of over 200 kHz. With this system, we demonstrate anactively stabilized linewidth of 525 Hz for our spectroscopy system. Using the upgraded cooling and spectroscopy laser systems, we demonstrate spectroscopy of the clock system and confirm temperature measurements derived from the transition linewidth. We also describe attempts to detect the recoil shift and 2-photon transition in neutral mercury.

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Environmental pollution has been a serious concern worldwide. Many degradation methods have been developed to clean sites contaminated with pollutants. More knowledge and better understanding in this field will help to protect our environment. The goal of the research in this thesis is to gain a better understanding of the mechanism of organic pollutant degradation in Fenton reactions and sonochemical reactions. Fenton degradation uses hydroxyl radical to oxidize organic compounds. The radical is produced by catalytic decomposition of hydrogen peroxide with Fe(II). Further research has found that addition of cyclodextrins can enhance degradation efficiency of hydrophobic organic pollutants. To study the mechanism of the enhancement, pollutant-cyclodextrin-Fe(II) aqueous systems were studied by fluorescence and NMR techniques. The results indicated the formation of pollutant/carboxymethyl-â-cyclodextrin/Fe(II) ternary complexes in the solution. With the ternary complex, the catalyst Fe(II) becomes closer to the pollutant, therefore leading to more efficient hydroxyl radical attack on the pollutant. Additional studies showed that hydropropyl-â- cyclodextrin, â-cyclodextrin and á-cyclodextrin bound pollutant well, but bound Fe(II) poorly. Sulfated-â-cyclodextrin did not bind well with pollutant although it bound Fe(II) well. Sonochemical degradation is another important pollutant treatment method in practice. It was found that phenol sonolysis can be enhanced by volatile hydrogen atom scavengers such as carbon tetrachloride and perfluorohexane. The non-volatile hydrogen atom scavenger iodate did not enhance phenol degradation. The first order rate constant for aqueous phenol degradation increased by about 2.2-2.8 times in the presence of 150 ìM carbon tetrachloride. In the presence of less than 1.5 ìM perfluorohexane the first order rate constant increased by about 2.3 times. Hydroquinone was the major observed reaction intermediate both in the presence and absence of hydrogen atom scavengers. Hydroquinone yields were substantially higher in the presence of hydrogen atom scavengers, suggesting that hydroxyl radical pathways for phenol degradation were enhanced by the hydrogen atom scavengers. The additives investigated in this study have potential to improve pollutant degradation efficiency. Other fields may also benefit from the information gained in this study. For example the improvement could be achieved in synthetic processes that rely on hydroxyl radical as a key intermediate.

O principal objetivo deste trabalho é, adotado uma abordagem centrada na simulação numérica, entender a desaceleração a laser de um feixe atômico por meio da conhecida técnica de ajuste Zeeman. Nossos cálculos numéricos são capazes de reproduzir as características fundamentais dos resultados experimentais já obtidos. Também apresentamos um modelo analítico simples incorporando as idéias básicas contidas nas hipóteses utilizadas nas simulações e mostrando que estas idéias são consistentes com as conclusões numéricas e experimentais. Isto demonstra que os aspectos essenciais do processo desacelerador são bem compreendidos. / The main purpose of this work is, adopting a numerical simulation approach, to understand the laser deceleration of an atomic beam by means 0f the kown Zeeman tuning technique. Our numerical calculations are able to reproduce the fundamental features of the experimental results already obtained. We also present a simple analytical model incorporating the basic ideas contained in the hypotheses used in the simulations, and show that these ideas are consistent with the numerical and experimental conclusions. This demonstrates that the essential aspects 0f the deceleration process are well comprehended.

Neste trabalho resultados experimentais inéditos da taxas de perdas para o sistema Cs-K em função da intensidade do laser de aprisionamento foram obtidos. A análise dos resultados foi auxiliada pelo modelo tipo Gallagher-Pritchard que demonstrou possuir uma dependência muito forte com a velocidade de escape. Um estudo complementar ajudou na determinação dos mecanismos causadores de perdas, a catálise óptica, onde o principal resultado foi a obtenção de um resultado teórico que corresponde a observação experimental para o sistema Na-Rb, onde as perdas foram associadas a atuação do estado duplamente excitado. Compreender os mecanismos causadores de perdas pode ajudar na construção de armadilhas magneto-ópticas de grande eficiência, importantes em experimentos de medidas de propriedades atômicas. / We have investigated trap loss rate as a function of trap laser intensity for the Cs-K system. A model based on Gallagher-Pritchard type considerations, allow understand the obtained results. To correctly interpret the data, we have proposed new mechanisms, which can be proven with recent experiment in Na-Rb system.

Over the last several years considerable efforts have been made to develop Bose-Einstein condensate (BEC) based devices for a number of applications including fundamental research, precision measurements, and navgation systems. These devices, capable of complex functionality, can be built from simpler components which is currently done in both optics and microelectronics. These components include cold atom equivalents of beamsplitters, mirrors, waveguides, diodes, and transistors. The operation of the individual components must be fully understood before they can be assembled into a more complex device. The primary goal of this dissertation is to present a theoretical analysis of these components. It begins with a theoretical analysis of several different types of cold-atom beamsplitters in the context of BEC interferometry. Next, the dynamics of an interferometer that uses optical pulses to control the dynamics of the BEC will be presented. Finally, a proposal for a BEC based component that has behavior that is similar to an electronic transistor is introduced.

Graphene, a one-atom-thick sheet of carbon atoms, is impermeable to all atoms and molecules; the same can be expected for other 2D crystals like hexagonal boron nitride (hBN). In this work we show that monolayers of graphene and hBN are highly permeable to thermal protons. As a reference, we show that monolayers of molybdenum disulphide as well as bilayers of graphene and tetralayers of hBN are not. Moreover, we show that water plays a crucial role in the transport mechanism. Because of the zero point energy of vibration in the oxygen-hydrogen bonds in water, protons face energy barriers smaller than previously predicted by theory. The effect, revealed by substituting hydrogen for deuterium, also shows that protons and deuterons transport at different rates across the membranes; establishing them as membranes with subatomic selectivity. Beyond the purely scientific implications, our results establish monolayers of graphene and hBN as a promising new class of proton conducting materials with potential applications in fuel cells, hydrogen purification and isotope enrichment technologies.

Silver (Ag) is a precious metal with a low stacking fault energy that is known to form copious nanoscale coherent twin boundaries during magnetron sputtering synthesis. Nanotwinned Ag metals are potentially attractive for creating new interface-dominated nanomaterials with unprecedented mechanical and physical properties. Grain-boundary segregation of solute elements has been found to increase the stability of interfaces and hardness of nanocrystalline metals. However, heavily alloying inevitably complicates the underlying deformation mechanisms due to the hardening effects of solutes, or a change of stacking fault energies in Ag caused by alloying. For the above reasons, we developed a microalloying (or doping) strategy by carefully selecting Cu as the primary impurity – a solute that is predicted to have no solid-solution strengthening effect in Ag when its content is below 3.0 wt.%. Neither will Cu affect the stacking fault energy of Ag at a concentration <1.0 wt.%. Moreover, Cu atoms are ~12% smaller than Ag ones, and Ag-Cu is an immiscible system, which facilitates the segregation of Cu into high-energy interface sites such as grain-boundaries and twin-boundary defects. In this thesis, large-scale hybrid Monte-Carlo and molecular dynamics simulations are used to study the unexplored mechanical behavior of Cu-segregated nanocrystalline nanotwinned Ag. First, the small-scale mechanics of solute Cu segregation and its effects on incipient plasticity mechanisms in nanotwinned Ag were studied. It was found that solute Cu atoms are segregated concurrently to grain boundaries and intrinsic twin-boundary kink-step defects. Low segregated Cu contents (< 1 at.%) are found to substantially increase twin-defect stability, leading to a pronounced rise in yield strength at 300 K. Second, atomistic simulations with a constant grain size of 45 nm and a wide range of twin boundary spacings were performed to investigate the Hall-Petch strength limit in nanocrystalline nanotwinned Ag containing either perfect or kinked twin boundaries. Three distinct strength regions were discovered as twin boundary decreases, delineated by normal Hall-Petch strengthening with a positive slope, the grain-boundary-dictated mechanism with near-zero Hall-Petch slope, and twin-boundary defect induced softening mechanism with a negative Hall-Petch slope. Third, by systematically studying smaller grain sizes, we find that the “strongest” size for pure nanotwinned Ag is achieved for a grain size of ~16 nm, below which softening occurs. The controlling plastic deformation mechanism changes from dislocation nucleation to grain boundary motion. This transition decreases to smaller grain sizes when Cu contents are segregated to the interfaces. Our simulations show that continuous Hall-Petch strengthening without softening, down to grain sizes as small as 6 nm, is reached when adding Cu atoms up to 12 at. %. For Cu contents ≥ 15 at. %, however, the predominant plastic deformation mechanism changes to shear-band induced softening. The present thesis provides new fundamental insights into solute segregation, and strengthening mechanisms mediated by grain boundaries and twin boundaries in face-centered cubic Ag metals, which is expected to motivate experimental studies on new nanotwinned metals with superior mechanical properties controlled by microalloying.

Atom chips are devices used to magnetically trap and manipulate ultracold atoms and Bose-Einstein condensates near a surface. In particular, permanent magnetic film atom chips can allow very tight confinement and intricate magnetic field designs while circumventing technical current noise. Research described in this thesis is focused on the development of a magnetic film atom chip, the production of Bose-Einstein condensates near the film surface, the characterisation of the associated magnetic potentials using rf spectroscopy of ultracold atoms and the realisation of a precision sensor based on splitting Bose-Einstein condensates in a double-well potential. The atom chip itself combines the edge of a perpendicularly magnetised GdTbFeCo film with a machined silver wire structure. A mirror magneto-optical trap collects up to 5 x 108 87Rb atoms beneath the chip surface. The current-carrying wires are then used to transfer the cloud of atoms to the magnetic film microtrap and radio frequency evaporative cooling is applied to produce Bose-Einstein condensates consisting of 1 x 105 atoms. We have identified small spatial magnetic field variations near the film surface that fragment the ultracold atom cloud. These variations originate from inhomogeneity in the film magnetisation and are characterised using a novel technique based on spatially resolved radio frequency spectroscopy of the atoms to map the magnetic field landscape over a large area. The observations agree with an analytic model for the spatial decay of random magnetic fields from the film surface. Bose-Einstein condensates in our unique potential landscape have been used as a precision sensor for potential gradients. We transfer the atoms to the central region of the chip which produces a double-well potential. A single BEC is formed far from the surface and is then dynamically split in two by moving the trap closer to the surface. After splitting, the population of atoms in each well is extremely sensitive to the asymmetry of the potential and can be used to sense tiny magnetic field gradients or changes in gravity on a small spatial scale.

<p>Södra Cell Mörrum is one of the five paper pulp plants that are included in Södra Cell, and the paper pulp that is produced here is not only sold to Swedish paper mills. Most of the paper pulp is exported to different countries in Europe. In the manufacturing process the plant needs different kind of process water and there are guideline values for how much copper, iron and sodium this water is allowed to contain. Analyzes of this water is in the current situation done with an atomic absorption spectrometric instrument (AAS-instrument) with a flame.</p><p> </p><p>Measurements done with flame-AAS of samples that have concentrations near the guideline values for copper, iron and sodium, are not reliable. The reason for not being reliable is that the quantitation limits of these metals are higher than the limit values. An alternative method that should give more reliable values is to analyze with an AAS- instrument with a graphite furnace. The purpose of this project was to perform a method validation of the graphite furnace of the AAS-instrument in the analysis of Cu, Fe and Na. The focus of the project was to find the detection limits for each metal, study the variation and to see if it is possible to analyze these water samples with this technique.</p><p> </p><p>The concentrations of the calibration solutions is between 1-10 µg/l for Na, 5-25 µg/l for Cu and 2-20 µg/l for Fe.The detection limits for all metals were slightly below 1 µg/l and during the present circumstances in the laboratory; it would be difficult to get even lower detection limits. There are improvements that can be done to get to the even lower detection limits. The results from this work show that the variation in each sampling cup is very small but if you look at different sampling cups the variation could be large if the cups are not treated in the right way. Further validation analyzes like variation in between days needs to be done.<strong> </strong></p><p>It is possible to analyze these low concentrations of copper, iron and sodium in the water samples with the AAS- graphite furnace, but it is difficult because there are many factors that affect the results. Examples of such factors are the environment where the instrument is placed in the laboratory and the human factor. Further analyzes needs to be done to get a better view of how these factors affect the result.</p>