This thesis is dealing with nanowires of zinc oxide and of cesium lead bromide. Main goal was a preparation of ZnO nanowires using MBE. This goal was partially achieved and growth of needle-like structures was observed. Another goal was characterization of already prepared ZnO nanowires. We successfully determined polarity of their surfaces, examined the influence of lattice defects and assessed the result of their doping. Side goal of this work was characterization of nanostructures of cesium lead bromide. However, preparation of cesium lead bromide nanowires remains an open issue.

Hydrotalcite-like compounds are synthetic anionic clays that have outstanding adsorption and catalytic properties. Hydrotalcite nanoclays (Mg–Al layered hydroxides) were synthesized by co-precipitation method. Obtained solids were converted into mixed metal oxides by thermal decomposition at temperatures up to 723 K. High adsorption and reconstructive properties of the mixed metal oxides allowed incorporating metal ions in their structure. Thus, these materials can be used as ion traps from aqueous media. Cesium ions were incorporated into hydrotalcite lamellar structure by impregnation method. Effects of different loads of Cs+ and adsorption times on the material properties were studied. The materials were characterized by X-ray diffraction, surface area analysis, scanning electron microscopy, energy dispersive X-ray spectrometry for obtaining a localized chemical analysis, and temperature-programmed desorption of CO2 for measurement of basic sites density. The amounts of metal incorporated in the structure was high enough due to small size of Cs+ ion. Synthetized materials also demonstrated high concentrations of strong surface basic sites formed through a synergistic effect of Cs and Mg ions. Basic properties of Cs-containing hydrotalcites enable their potential use as catalysts of base-catalyzed reactions.

An adsorbent for Cs removal from contaminated water based on phosphotungstic acid (PTA) embedded in SiO 2 network was synthesized and granulated with γ-Al 2 O 3 . PTA/SiO 2 had a high adsorption capacity towards Cs while the binder provided excellent mechanical characteristics of the material. It was shown that small particles of PTA/SiO 2 with the sizes of 0.1–1 µm occupied space between larger particles of the binder (up to 5 µm). Chemical interaction between PTA and γ-Al 2 O 3 during the adsorbent preparation also took place. The obtained porous material with the specific surface area of 286.9 m 2 /g contained 4.73% of PTA. Presence of Keggin units in the structure was confirmed by solid state NMR spectroscopy. Study of the adsorbent in Cs + adsorption from solutions demonstrated its high adsorption capacity. The concentrations of Cs + in the solutions after the column tests decreased by 3.3–5.2 times. The presence of Na + and K + as competing ions did not affect the adsorption. The material was tested in clean-up of radioactive water from the shelter of Chernobyl nuclear power plant (Ukraine). A significant decrease of 137 Cs radioactivity was detected in all samples of radioactive water, especially in acidic solutions. Thus the adsorbent can be used for water treatment after incidents resulting in release of radioactive isotopes 134 Cs and 137 Cs.

The adsorption of cesium on mesoporous silica materials containing embedded phosphotungstic acid (PTA) was studied. The materials contained active adsorbent and binders: γ-Al2O3, kaolin, or charcoal. The presence of Keggin units of PTA in the bound materials was confirmed by FT-IR spectroscopy. Among all materials, the formulation with γ-Al2O3 demonstrated the highest porosity and effectiveness in adsorption. Pure PTA/SiO2 contained a significant fraction of small particles between 100 and 300 nm. However, in the alumina-bound material, they were not detected. SEM imaging showed that these particles occupied interparticle space between larger γ-Al2O3 particles. The material was stable up to 540 °C. In most materials, the adsorption of cesium decreased with increase of the binder contents but not proportionally. The adsorption capacity of all materials depended on the concentration of cesium in the solutions. Maximum adsorption was achieved after 1 h. The adsorption of cesium is controlled by intraparticle diffusion while its rate can be described by the pseudo-second-order model.

A new spectrometric technique for measuring diffusion coefficients of Ordovician Queenston Formation shale from the Michigan Basin of southwest Ontario, Canada is presented; in this case pore diffusion coefficients (Dp) were determined for the conservative (iodide, I^-) and reactive (cesium, Cs^+) tracers in porous media. Furthermore, diffusion-reaction parameters such as Cation exchange capacity (CEC) were obtained for the reactive tracer, Cs^+ by the reactive-transport modeling. The principle of X-ray absorption spectrometry (XAS) is based on the attenuation of high atomic number of diffusive species (e.g. Cs^+and I^-) in porous media, allowing for the quantification of the resulting spatial changes. The technique employs a 1.1 mm collimated X-ray beam to resolve the tracer presence in a slice; small region of a rotating sample for a fixed time. The x-ray beam is incident on a sample of porous rock while the transmitted beam is detected on the opposite side of the sample, allowing acquisition of a transmitted X-ray energy spectrum vs intensity (counts). Additional analyses such as mineralogical studies by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) were conducted to improve the understanding of solute transport. The comparison of the data obtained by the XAS method indicating a good agreement with established radiography and other conventional diffusion methods provide an alternate approach for quantifying the diffusion coefficient of porous media.

Atomic beam magnetic resonance techniques have been used to investigate the properties of the 41-second isomeric state of silver-109 and the 32-minute ground state of the fission product cesium-138. A description of the apparatus and of the atomic beam method for the determination of nuclear moments is given. The results obtained for silver-109m are: I= 7/2 a(2S1/2) = 9477±13 Mc/sec μ1 (uncorrected) = 4.31±0.04 nuclear magnetons 109Δ109m = -(1.1±1.2)%. The value of the moment confirms that the proton configuration is (g9/2)^-3 7/2. In the course of this experiment, multiple quantum Zeeman transitions were observed between levels in both the F = I + 1/2 and F = I - 1/2 hyperfine multiplets. The results obtained for cesium-138 are: I =3 Δv = 1650 +650 -250 Mc/sec |μI| (uncorrected)= 0.45 +0.18 -0.07 nuclear magnetons. For these experiments simultaneous detection of both the resonant and thrown out portions of the beam was used for the first time in this laboratory. / Thesis / Doctor of Philosophy (PhD)

Thermal methods of high precision were used to determine the solid-liquid phase equilibria diagrams for the potassium-rubidium and the rubidium-cesium systems. Both form minima in the liquidus curves occurring at 307.00° K with 0.667 mole fraction rubidium in the potassium-rubidium system and 282.85° K with 0.530 mole fraction cesium in the rubidium-cesium system. In the potassium-rubidium system, the liquidus and solidus points are very close together, giving a very narrow temperature range for the two phase region. The freezing point minimum in the potassium-rubidium system occurs at 0.667 mole fraction rubidium, suggesting the possible formation of a KRb2 intermetallic compound.

In preparation for the large backgrounds expected to be present in the Belle II detector from the SuperKEKB e+e- collider, the radiation hardness of several large (5 x 5 x 30 cm3) thallium doped cesium iodide (CsI(Tl)) scintillation crystals are studied. The crystal samples studied consist of 2 spare crystals from the Belle experiment using PIN diode readout and 7 spare crystals from the BaBar experiment using photomultiplier tube readout. The radiation hardness of the scintillation properties of the CsI(Tl) crystals was studied at accumulated 1 MeV photon doses of 2, 10 and 35 Gy. At each dose, the longitudinal uniformity of the crystals light yield, scintillation decay times, time resolution and energy resolution was measured. As the Belle II collaboration is considering an upgrade to pure CsI crystals if CsI(Tl) does not satisfy radiation hardness requirements, the scintillation properties of a pure CsI scintillation crystal were also measured and compared to the CsI(Tl) crystal measurements. In addition to experimental work, Monte Carlo simulations using GEANT4 were written to compare ideal pure CsI and CsI(Tl) crystals and to study the effects of radiation damage on the performance of the Belle II electromagnetic calorimeter. / Graduate

We demonstrate a resonance imaging protocol for optical lattices that enables robust preparation and single qubit addressing of atoms with sub-wavelength resolution in 1D. A 3D optical lattice consisting of three sets of independent 1D counter- propagating laser beams provides the trapping potential for the atoms. On this optical lattice platform, a long-period 1D superlattice is imposed by interfering two laser beams at a shallow angle centered at the atoms. This superlattice creates a position-dependent shift of the qubit transition frequency defined between two spin states in the ground manifold. Isolated 2D planes of atoms are prepared by flipping the resonant spins with a microwave pulse and removing the non-resonant spins by pushing them out of the lattice with a resonant laser beam. The periodic planes of atoms that are prepared can be imaged by applying another microwave pulse and detecting the fluorescence from the spins that flip back to the initial state, as a function of superlattice displacement between the preparation and read-out pulses. By employing these new techniques for sub-wavelength imaging, we tested the effectiveness of using composite pulses for addressing the trapped atoms in an optical lattice. Composite pulse techniques can be used to reduce the sensitivity of the addressing to small variations in the relative position and intensity of the lattices. This robustness is achieved by applying numerically generated composite pulses that have a constant atomic response within a target range of relative lattice positions and intensities. We designed a composite microwave pulse that flips the spin with near unit fidelity for all atoms that are positioned within a target spatial region, while conserving the spin of the atoms outside of that region. This cannot be accomplished with plain pulses due to off-resonant excitation. We also expanded the concept of this technique for robustly addressing spins even further to implement independent unitaries, or single qubit quantum gates, across several adjacent lattice sites. Finally, in order to quantitatively measure the fidelity of these robust composite pulses, we perform a randomized benchmarking procedure, which was first proposed by Knill.

No description available.