The Infrared absorption of a single crystal of portlandite, over a temperature range from room temperature to below the melting point of hydrogen, was studied with both polarized and unpolarized radiation. The apparatus and experimental techniques are described, and the results and their significance in relation to earlier experimental work on the crystal structure of portlandite are discussed. / Thesis / Master of Science (MS)

The ¹A₂ ← ¹A₁ (π* ← n) electronic absorption spectrum of thioformaldehyde vapour has been investigated. The six excited state fundamental frequencies for both CH₂S and CD₂S are determined from the vibrational analysis. The three rotation constants and three symmetric top distortion constants for the 0⁰₀, 4¹₀ and 3¹₀4³₀ bands of CH₂S and the 0⁰₀, 4¹₀ and 5¹₀ bands of CD2S are determined from a least squares rotational analysis of these bands. The rotational constants of the 0⁰₀ and 4¹₀ bands of CH₂S and CD₂S are used to determine the structure of the molecule in the excited state. / Thesis / Doctor of Philosophy (PhD)

Un changement de pH peut induire une modification des propriétés chimiques et physiques des molécules, par exemple leur interaction avec la lumière. La modélisation de tels phénomènes est complexe en raison de l’ensemble statistique des états de protonation microscopiques et de la nature quantique de la propriété étudiée. Dans cette thèse, nous présentons un protocole de calcul qui associe une méthode capable d'échantillonner à la fois ces micro-états et les changements structuraux à un pH donné, et un cadre traitant la partie pertinente de la macromolécule avec des traitements avancés de mécanique quantique et le reste du système avec la mécanique moléculaire classique. Nous rapportons également la validation de ce protocole sur le relativement petit peptide M et son application à la rhodopsine sensorielle d'Anabaena, une protéine microbienne. Nous avons pu révéler quels sont les acides aminés titrables responsables du spectre d'absorption dépendant du pH de cette biomolécule / A change in the pH can modify the chemical and physical properties of molecules such as the way they interact with light. Modeling such phenomena is complex, because of the statistical ensemble of microscopic protonation states and of the very quantum nature of the property of interest. In this thesis, we present a computational protocol which merges a method capable of sampling at the same time these microstates and the structural changes at a given pH, and a framework treating the relevant portion of the macromolecule with advanced quantum mechanics treatments and the rest of the system with classical molecular mechanics. We also report the validation of this protocol on the relatively small peptide M and its application to the anabaena sensory rhodopsin, a microbial protein. We have revealed which are the titratable amino-acids responsible for the pH-dependent absorption spectrum of this biomolecule

Since the discovery of cuprate superconductors, PrBa2Cu3O7 (Pr123) has attracted much attention due to its nonsuperconductivity and other anomalies. The very recent reports on superconducting Pr123 instead of putting an end of this issue, virtually stimulate more controversies. One of the proposed explanations for the recently observed superconductivity in Pr123 is that the samples could be Ba-rich Pr123 to investigate this possibility, we prepared Pr1-xBa2+xCu3O7 (x=1~0.3) and Pr1-xCaxBa2Cu3O7 (x=0~0.6) as comparison. X-ray absorption near edge spectroscopy (XANES) indicates an increase in carrier concentration with Ba and Ca doping, which is consistent with resistivity and thermoelectric power(TEP) data. However, carriers are introduced in a peculiar why rather than simply add into CuO2 plane.

Structural evolution and its effect on optical absorption/emission behavior of fluorene-thiophene conjugated alternate copolymers and naphthalene-thiophene conjugated alternate copolymers and polystyrene-poly-3octylthiophene-polystyrene triblock copolymer of upon isothermal heat treatment at elevated temperatures, and the well £k-£k stack at interchain species (ordered aggregates) be formed in dilute solutions and its effect the UV-vis and PL spectra. These conjugated polymer with mono- or disubstituted with alkyl side chain and with alkyl or alkoxyl flexible side-chains. This studied by means of a combination of polarized light microscopy, x-ray diffraction, ultraviolet-visible spectroscopy, light scattering spectroscopy and photoluminescence spectroscopy. According to the results of the experiment, the fluorene-based polymer can be observed emission from order aggregate in the solution state, but not found in naphthalene-based and triblock copolymer.

This thesis is a study of the near infra-red absorption spectrum of ethylidene fluoride.

Optical absorption spectra of alkali halide crystals containing H⁻ ions (U-centres) are calculated using a two-parameter model to describe the defect. It is shown that this model gives a satisfactory account of the observed anharmonic sideband of the main U-centre absorption band in the infrared, and also of the impurity-induced far infrared absorption for the two host crystals considered, potassium bromide and potassium iodide. The broadening of localized modes and resonances is also discussed. In particular, the anharmonic broadening is calculated for the main U-centre line in KI and KBr and for a localized gap mode in KI:KH. / Thesis / Doctor of Philosophy (PhD)

<p> The results of an investigation of the electronic absorption spectrum of carbon diselenide are presented. The synthesis of the compound from individual isotopes of selenium is described.. Some new observations and results from a reinvestigation of the infrared and Raman spectra are reported. The electronic absorption spectra of individual isotopic molecules were recorded and a detailed vibrational analysis of one of the observed systems in the spectrum has been made o The rotational structure of bands in this system has been examined. A preliminary study of two other systems are discussed. The spectra of carbon diselenide and the analogous carbon disulphide are compared and the similarity between the two spectra is shown. </p> / Thesis / Doctor of Philosophy (PhD)

Neste trabalho estudamos as propriedades estruturais e eletrônicas do CO2 supercrítico, iniciando com a avaliação de campos de força balizados por aplicações anteriores de simulação quântica do tipo Dinâmica Molecular de Born-Oppenheimer (BOMD). A aplicação principal é a descrição do espectro de absorção da paranitroanilina (pNA) em CO2 supercrítico. O CO2 supercrítico pode ser considerado como uma ``alternativa verde para os solventes orgânicos convencionais e a busca por solventes mais seguros, juntamente com a crescente consciência sobre a questão ambiental, tem levado a uma ``química verde com o intuito de se buscar soluções sustentáveis. A princípio estudamos três campos de força tradicionais para o CO2, aplicados na região supercrítica. Estes campos de força podem ser validados por meio de simulação de primeiros principios. Iniciamos considerando a condição supercrítica para o CO2 como T = 315 K, = 0.81 g/cm³ e o campo de força clássico de Zhang e Duan. Depois fizemos uma análise consistindo de uma alteração de cargas e também da geometria do CO2, que seria um caso não linear no qual foi considerado um ângulo (O-C-O) = 176° . O estudo do solvatocromismo da pNA em CO2 supercrítico foi feito considerando todas estas situações descritas para o campo de força, avaliando os resultados experimentais e teóricos já existentes. A simulação gera estruturas usando Monte Carlo e são usadas em cálculos de Mecânica Quântica do tipo DFT (CAM-B3LYP). Por fim, para verificar a importância da geometria do sistema, ou seja, a propriedade estrutural, consideramos uma outra geometria para a pNA, diferente da geometria que utilizamos a princípio nas simulações com o CO2 supercrítico. Essa ``geometria modificada\" da pNA foi obtida de uma simulação existente de Born-Oppenheimer e a utilizamos numa simulação Monte Carlo com o caso não linear para o CO2 supercrítico. Os resultados de todas essas simulações nos indicaram que a alteração das cargas e por consequência a alteração da polarização do solvente, não possui muita importância na mudança do espectro de absorção da pNA. Ao se considerar o CO2 não linear, obtivemos resultados um pouco melhor, mas não muito, comparados com a previsão teórica. Mas os resultados mais significativos são os obtidos para a situação em que utilizamos a geometria modificada da pNA. Uma parte do deslocamento do máximo da banda de absorção no espectro da pNA vem com a contribuição eletrostática da interação soluto-solvente e a outra parte vem da mudança estrutural. / In this work we study the structural and electronic properties of CO2 supercritical starting with the evaluation of force fields based on previous ab initio Born-Oppenheimer molecular dynamics (BOMD). The main application is the description of the absorption spectrum of paranitroanilina (pNA) in supercritical CO2. The supercritical CO2 is considered a ``green alternative\" to conventional organic solvents and the search for safer solvents, along with the increasing awareness of environmental issues has led to the interest in ``green chemistry\", seeking sustainable solutions. At first we studied three traditional force fields for CO2, applied in the supercritical region. These force fields can be validated by first principles simulation. We considered the supercritical condition for CO2 as T=315K, =0.81g/cm³ and the classical force field of Zhang and Duan. We also did an analysis consisting of a change of the atomic point charges and the geometry of CO2, including a non-linear case in which an angle (O-C-O)=176° was considered. The study of the solvatochromism of pNA in supercritical CO2 was made considering all these situations, evaluating the theoretical outcome and the experimental results. The simulation generates structures using Monte Carlo and are used in quantum mechanics calculations of DFT (CAM-B3LYP). To verify the importance of geometry in the system, that is, the structural property, we considered another geometry for the pNA geometry different from that we used initially in the simulations with supercritical CO2. This ``modified geometry\" of pNA was obtained from a previous Born-Oppenheimer simulation and was used in a Monte Carlo simulation with the non-linear case for supercritical CO2. The results of all these simulations indicated that the alterations of charge and thus the change in the polarization of the solvent, has no great importance in the change of the absorption spectrum of the pNA. When considering the nonlinear CO2, we obtained slightly better results. But the most significant results are obtained for the situation in which we use the modified geometry of pNA. Part of the shift in the absorption spectrum of the pNA comes with the electrostatic contribution of solute-solvent interaction and the other part comes from the structural change.

O complexo formado pela molécula de tetraciclina com o íon de magnésio é capaz de impedir a replicação do material genético no ribossomo bacteriano, tornando a tetraciclina um excelente antibiótico. Outra aplicação da tetraciclina, ligada ao íon európio, consiste em estimar a concentração de colesterol no sangue a partir das mudanças do espectro de emissão. Tal técnica apresenta uma resposta imediata e confiável, comparada às técnicas atuais. Emgeral, o espectro de absorção e emissão da tetraciclina é bastante sensível aos íons alojados e ao pH do solvente que o conjunto está imerso. Entretanto, o espectro de absorção teórico em solvente foi obtido com simples modelos contínuos que não consideram interações específicas impostas pelo ambiente no líquido, além da escassez de estudos teóricos para os complexos. Nossa proposta é obter o espectro de absorção eletrônica da tetraciclina e dos complexos formados com os íons Mg e Eu. Além disso, analisamos as mudanças de intensidade e deslocamentos dos máximos das bandas nos sistemas mencionados, em função do pH do solvente e do posicionamento do íon, estimando seu correto posicionamento. Realizamos a simulação clássica usando a técnica de Monte Carlo aplicando o potencial de Lennard-Jones mais Coulomb para cada átomo da molécula de tetraciclina e dos complexos em água. O espectro de absorção eletrônica foi obtido a partir da teoria funcional da densidade dependente do tempo considerando diversos modelos para descrição do solvente e do íon. Em geral, obtivemos uma boa descrição qualitativa dos espectros, quando comparado com os resultados experimentais. Os deslocamentos das bandas e mudanças de intensidades foram bem descritos pelos modelos que utilizaram a simulação clássica para gerar as configurações. Porém cada modelo privilegiou uma propriedade de um determinado sistema, tanto para as diferentes formas da tetraciclina quanto para a presença de íons. Palavras-chaves: tetraciclina, magnésio-tetraciclina, európio-tetraciclina, espectro de absorção, teoria do funcional da densidade dependente do tempo, simulação por Monte Carlo / The complex formed by the tetracycline molecule with the magnesium ion is able to avoid the replication of the genetic material in bacterial ribosome, making tetracycline an excellent antibiotic. Another application of tetracycline attached to the europium ion, is to evaluate the concentration of cholesterol in the blood from the changes in the emission spectrum. This technique presents an immediate and reliable response compared to current techniques. In general, the absorption and emission spectrum of tetracycline is sensitive to ions coupled and the pH of the solvent that the complex is immersed. However, the theoretical absorption spectrum in solvent was obtained with simple continuum models that do not consider specific interactions imposed by the liquid environment, and also the lack of theoretical studies for the complexes. Our proposal is to obtain the electronic absorption spectrum of tetracycline and complexes formed with the ions Mg and Eu. In addition, we analyze the changes in intensity and peak shifts of the bands in the systems mentioned as the function of pH of the solvent and the position of the ion, and estimating the correct position of the ion. We performed a simulation using the classical Monte Carlo technique applying the Lennard-Jones plus Coulomb potential for each atom of the molecule tetracycline and complexes in water. The electronic absorption spectrum was obtained with the time dependent density functional theory considering several models to describe the solvent and ion. In general, we obtained a good qualitative description of the spectra when compared to the experimental results. The shift of the bands and intensity changes were well described by the used models on classical simulation. However, each model favored one property of the system, both for the different forms of tetracycline and for the presence of ions. Keywords: tetracycline, magnesium-tetracycline, europium-tetracycline, absorption spectrum, time dependent density functional theory, Monte Carlo simulation