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The main objective was to develop a procedure based on differential optical absorption spectroscopy (DOAS) to measure atmospheric total column of ozone, using the automated instrument developed at the University of North Texas (UNT) by Nebgen in 2006. This project also explored the ability of this instrument to provide measurements of atmospheric total column nitrogen dioxide. The instrument is located on top of UNT’s Environmental Education, Science and Technology Building. It employs a low cost spectrometer coupled with fiber optics, which are aimed at the sun to collect solar radiation. Measurements taken throughout the day with this instrument exhibited a large variability. The DOAS procedure derives total column ozone from the analysis of daily DOAS Langley plots. This plot relates the measured differential column to the airmass factor. The use of such plots is conditioned by the time the concentration of ozone remains constant. Observations of ozone are typically conducted throughout the day. Observations of total column ozone were conducted for 5 months. Values were derived from both DOAS and Nebgen’s procedure and compared to satellite data. Although differences observed from both procedures to satellite data were similar, the variability found in measurements was reduced from 70 Dobson units, with Nebgen’s procedure, to 4 Dobson units, with the DOAS procedure.A methodology to measure atmospheric nitrogen dioxide using DOAS was also investigated. Although a similar approach to ozone measurements could be applied, it was found that such measurements were limited by the amount of solar radiation collected by the instrument. Observations of nitrogen dioxide are typically conducted near sunrise or sunset, when solar radiation experiences most of the atmospheric absorption.

<p> The optical absorption in manganese fluoride has been studied in the range of 30 to 300 cm^-1 with emphasis placed on the possible multiple magnon absorptions (other than two-magnon) and an induced single magnon absorption. It is shown that theoretically one can expect four-magnon processes by expanding the Heisenberg spin hamiltonian to higher orders in the creation and annihilation operators introduced by the Holstein-Primakoff transformation. However, neither an induced one magnon nor four magnon process was observed. The absorptions which were seen in the spectra were attributed to phonon processes.</p> / Thesis / Master of Science (MSc)

This dissertation deals with the characterization of the nonlinear absorption and refraction of two representative metallophthalocyanine dyes: chloro aluminum phthalocyanine dissolved in methanol, referred to as CAP, and a silicon naphthalocyanine derivative dissolved in toluene, referred to as SiNc. Using the Z-scan technique, the experiments are performed on both the picosecond and nanosecond timescales at a wavelength of 0.532 μm.

Glasses in the system v₂o₅-Te0₂ were prepared at intervals throughout the glass-forming composition range. The vanadium valence state was varied for each composition by the addition of elemental tellurium to reduce the melt. A chemical analysis method was devised to determine the v⁴⁺:vtotal ratio. Conductivity and thermopower measurements were made as functions of composition, valence ratio and temperature. The conductivity was found to increase as the total vanadium content increased and to be 21/2 to 3 orders of magnitude greater than that of a v₂0₅-P₂0₅ glass of similar v₂o₅ content. A maximum in conductivity was observed as the vanadium valence ratio was varied. This maximum was shifted to values around v⁴⁺:vtotal = 0.2 from the theoretically predicted value of 0.5. At temperatures above 250 K the conductivity varied exponentially with temperature with activation energies in the range 0.25 to 0.40 eV. Below this temperature there was a continuous decrease in slope of the conductivity down to the lowest temperature at which measurements were made. Thermopower was found to be negative and temperature independent above 250 K, while below this temperature it decreased in an activated manner with an activation energy of 0.02 eV. As a function of valence ratio the thermopower followed the behaviour predicted by Heikes and Ure, with the exception that the change of sign occurred at v⁴⁺:vtot ratios of around 0.2, instead of the theoretically predicted value of 0.5. (iii) Measurements were made of the optical absorption coefficient as functions of photon energy, composition, valence ratio and temperature. Temperature and composition did not affect the absorption spectrum significantly except that an absorption band appeared below the fundamental absorption edge as the glasses were reduced. The high electric field and a.c. properties of the glasses were also measured. These are consistent with hopping conduction of carriers between v⁴⁺ and v⁵⁺ sites. This data gives indirect indications of an inhomogeneous glass structure.

Este trabalho teve por objetivo o preparo e estudo das propriedades de vidros fotocrômicos. Foram preparados vidros de aluminoborosilicatos de potássio (40\'SI\'\'O IND. 2\'.10\'AL IND. 2\'\'O IND. 3\'.(50-x)\'B IND. 2\'\'O IND. 3\'.X\'K IND. 2\'\'O\'- 14,9 < x < 17,7) dopados com \'AG\'\'CL\' e \'CU POT. 2+\'. As amostras foram fundidas em cadinho de platina, em forno de elementos resistivos de \'SI\'\'C\', a \'1400 GRAUS\'C por duas horas, sendo derramados sobre molde de aço inoxidável. Uma tentativa de análise química quantitativa dos componentes após a fusão foi feita por Retroespalhamento de Rutherford. A proporção de prata retida no vidro foi determinada por este método. Medidas de dilatometria e densidade foram feitas para amostras de composição base diferentes. As medidas de dilatometria permitem a obtenção do coeficiente de dilatação térmica, e os parâmetros típicos de vidros conhecidos como: temperatura de transição vítrea e temperatura de \"softening dilatométrico\". Tratamentos térmicos em temperaturas próximas do ponto de amolecimento (softening point) provocam a precipitação de partículas coloidais de \'AG\'\'CL\' na matriz vítrea. Estas são responsáveis pelo comportamento fotocrômico dos vidros. Fatias de uma amostra foram submetidas a programas de tratamento térmico de 0,5 h a várias temperaturas entre \'480 GRAUS\'C e \'620 GRAUS\'C e programas de vários intervalos de tempo entre 0,25 e 1,25h a \'600 GRAUS\'C. As propriedades de absorção óptica das várias fatias, antes e depois de exposição à luz UV, foram comparadas. As características morfológicas das partículas coloidais de \'AG\'\'CL\' produzidas pelos tratamentos térmicos foram investigadas por SAXS. Os raios R das partículas mostraram uma relação linear com a temperatura para tratamentos de 0,5 h entre 550 e \'620 GRAUS\'C e uma relação linear de \'R POT. 3\' com o tempo de tratamento a \'600 GRAUS\'C. Duas séries de amostras foram preparadas para estudar: 1. a influência da quantidade de cobre 2. a influência da proporção de \'K IND. 2\'\'O\' em relação a \'B IND. 2\'\'O IND. 3\'. As propriedades de absorção óptica (antes e depois de exposição à luz UV) das amostras das duas séries, submetidas a tratamentos térmicos a \'600 GRAUS\'C por diversos tempos entre 0,25 e 1,6 h foram comparadas. / The purpose of the present work was to prepare and study the properties of photochromic glasses. Potassium aluminoborosilicate glasses (40\'SI\'\'O IND. 2\'.10\'AL IND. 2\'\'O IND. 3\'.(50-x)\'B IND. 2\'\'O IND. 3\'.X\'K IND. 2\'\'O\'- 14,9 < x < 17,7) doped with \'AG\'\'CL\' and \'CU POT. 2+\' were prepared. The samples were melted in platinum crucible, in electric furnace with silicon carbide resistences, at \'1400 GRAUS\'C for two hours, and poured on stainless steel mold. An attempt to perform a quantitative chemical analisis of the components after melting was carried out by Rutherford Backscattering method. The amount of silver incorporated into the glass was determined by this method. Measurements of dilatometry and density were performed for samples of different base composition. The dilatometric measurements give the thermal expansion coefficient, and the typical glass parameters such as glass transition point and dilatometric softening point. Thermal treatments at temperatures near the softening point precipitate colloidal \'AG\'\'CL\' particles in the glass matrix. These particles are responsible for the photochromic characteristics of the glass. Slices of a sample were submitted to thermal treatments for 0.5 hours at temperatures between 480 and \'620 GRAUS\'C and treatments at \'600 GRAUS\'C for several) time intervals between 0.25 and 1.25 hours. The optical absorption properties of these slices, before and after UV light exposure, were compared. The morphological aspects of the \'AG\'\'CL\' coloidal particles were investigated by SAXS. The particle radii R presented a linear relation with the temperature for treatments for 0.5 hour at temperatures between 550 and \'620 GRAUS\'C and a linear relation of \'R POT. 3\' with time for treatments at \'600 GRAUS\'C. Two sample series were prepared to investigate: 1. the influence of the amount of copper 2. the influence of the amount of \'K IND. 2\'\'O\' in relation to the amout of \'B IND. 2\'\'O IND. 3\' The optical absorbances (before and after exposure to UV light) for samples of the two series, annealed at \'600 GRAUS\'C for different times between 0.25 and 1.6 hours were compared.

Advances in optical imaging techniques have allowed quantitative studies of many biological systems. This dissertation elaborates on our efforts in both developing novel imaging modalities based on detection of optical absorption and applying high-sensitivity fluorescence microscopy to the study of biology. / Chemistry and Chemical Biology

Highly sensitive magneto-optical techniques have been used to investigate weak linear and nonlinear optical absorption mechanisms in p- and n-type InSb. As a result, new absorption processes involving both impurities and free carriers have been identified and studied in detail. For p-InSb, magneto-optical spectra has been obtained over a wide range of temperatures and photon energies. The spectra obtained at higher sample temperatures are seen to result from combined-resonance transitions of free holes between heavy-and light-hole Landau levels, while bound-hole transitions between ground heavy-hole-like and excited light-hole-like acceptor states are observed at lower temperatures. Analysis of the combined-resonance data along with extensive intra-conduction band and two-photon interband data using a modified Pidgeon and Brown 8X8 energy band model has allowed the determination of a single set of band parameters for InSb that quantitatively describes these different sets of data. In addition, a ground state binding energy of 8.1 meV for Cd acceptors and 42.5 meV for Au acceptors has been extracted from the analysis of the bound-hole spectra. For n-lnSb, photo-Hall techniques have been developed and used to study both resonant impurity and two-photon magneto-absorption (TPMA) processes in detail. As a result, LO-phonon-assisted impurity cyclotron resonance harmonic (LOICRH) transitions from the shallow Te donor level have been observed for the first time. In addition, transitions from deep levels are also observed in the photo-Hall signal obtained at sample temperatures greater than 20K. Both time-resolved and intensity-dependent measurements on impurity and TPMA processes are reported and the results compared directly with the predictions of rate equations describing the photoexcited carrier dynamics. These investigations have yielded important information about the optical properties of n-InSb; e.g. impurity and two-photon absorption coefficients, photo-excited carrier lifetimes, and recombination rates.