Many of the bands in the vapor-phase far-ultraviolet absorption spectra of simple molecules can often be fit to mathematical progressions referred to as molecular Rydberg series. The name Rydberg arises from the similarity between the Rydberg formula for the atomic hydrogen spectrum and the formulae for the progressions found in molecular spectra. The theories of molecular Rydberg transitions and states are discussed in terms of the inferences that have been made in the past from the available spectral data. The dipole moment changes (ca. 0.4 Debye units) from the ground state to all of the Rydberg states studied were found to be smaller than changes typically found in transitions of charge-transfer nature (ca. 1 Debye unit). The implication is that the Rydberg transitions are fairly localized. The changes in polarizability are on the order of 6 x 10⁻²⁴ cm³ and are assumed to be increases over those of the ground state.

InAs/InP multiwavelength quantum dash lasers are promising solutions to rising data loads in our telecommunications systems, as one laser chip can replace many lasers operating at a single wavelength. Quantum dashes are quasi-one-dimensional nanoparticles that offer equal or increased performance as laser gain media when compared to equivalent quantum well devices. InAs/InP quantum dashes are ideal for laser devices emitting in the C-band region, centred around 1550 nm. The quantum dashes in this thesis are epitaxially grown via the self assembled Stranski-Krastanow mode. Characterizing how structure and composition of these quantum dashes affect the energy level spacing and emission wavelengths is crucial for designing better performing telecommunications lasers. In this thesis a method for determining the average heights and widths of these nanoparticles from atomic force microscopy measurements of uncapped InAs/InGaAsP/InP quantum dashes is developed. Single quantum dash simulations are built in Crosslight Photonic Integrated Circuit Simulator (PICS3D) with the lowest energy transition tuned to photoluminescence peak wavelengths provided by National Research Council Canada. These simulations are used to determine the impact of quantum dash dimensions, compositions, and heterostructure changes to the overlap integrals and emission energies. Phosphorus concentration within the quantum dash and wetting layer can modify the predicted emission wavelength by ∼200 nm, and increasing quantum dash lengths beyond 200 nm has negligible effect on emission energy and energy level spacing. The sublayer thickness is increased from 0.1 to 1 nm, and shows that emission energy will increase for GaP sublayers and decrease for GaAs sublayers by up to 30 meV. The role of the wetting layer on energy level spacing is discussed and determined to increase the emission energy by ∼15 meV when the 0.5 nm wetting layer is removed for a 2 nm quantum dash. The role of As/P intermixing is investigated in three ways: by incorporating phosphorus concentration in (1) the quantum dash and wetting layer, (2) the wetting layer, and (3) the lower portion of the quantum dash without a wetting layer. There is negligible change in the overlap integral for these three cases with all other variables held constant, and the trends between each case remain the same. Further experimental analysis of buried InAs quantum dashes is recommended for compositional information. The implementation of variable strain profiles in this model is also recommended, in addition to developing vertically coupled quantum dash simulations. Finally, performing these simulations at varying temperatures will better represent the operating conditions of quantum dash lasers.

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The rotational microwave spectra of the three isotopes (^13CH_3^12C^15N, ^12CH_3^13C^15N, and ^13CH_3^13C^15N) of the methyl cyanide molecule in the v_8=3, v_8=2, v_7=1 and v_4=1 vibrational energy levels for the rotational components 1£J£5 (for a range of frequency 17-95 GHz.) were experimentally and theoretically examined. Rotational components in each vibration were measured to determine the mutual interactions in each vibration between any of the vibrational levels investigated. The method of isotopic substitution was employed for internal tuning of each vibrational level by single and double substitution of ^13C in the two sites of the molecule. It was found that relative frequencies within each vibration with respect to another vibration were shifted in a systematic way. The results given in this work were interpreted on the basis of these energy shifts. Large departure between experimentally measured and theoretically predicted frequency for the quantum sets (J, K=±l, ϑ=±1), Kϑ-l in the v_8=3 vibrational states for the ^13c and ^15N tagged isotopes of CH_3CN showed anomalous behavior which was explained as being due to Fermi resonance. Accidently strong resonances (ASR) were introduced to account for some departures which were not explained by Fermi resonance.

A energia não adiabática do estado fundamental para o átomo de hélio é obtida com o formalismo adiabático hiperesférico (HAA). Curvas de potencial, acoplamentos não adiabáticos e funções de canal são calculados por um procedimento numericamente exato baseado em uma expansão analítica das funções de canal. As equações radiais acopladas são resolvidas por técnicas usuais. A convergência do procedimento é investigada conforme os acoplamentos não adiabáticos são sistematicamente introduzidos. Com a inclusão, pela primeira vez, de onze curvas de potencial e funções de canal obtém-se uma energia para o estado fundamental que difere do melhor cálculo variacional por 0.1 partes por milhão. As forças de oscilador para as transições discretas do hélio na \"length-form\" e \"acceleration-form\" também são calculadas. Concluímos que o HAA não está mais obstruído pela falta de uma prescrição para se obter funções de onda de precisão arbitrária para sistemas coulombianos. / The nonadiabatic ground state for the helium atom is obtained with the hyperspherical adiabatic approach (HAA). Potential curves, nonadiabatic couplings, and channel functions are calculated by a numerically exact procedure based on the analytical expansion of the channel functions. The coupled radial equations are solved by standard techniques. The convergence of the procedure is investigated as nonadiabatic couplings are systematically introduced. The inclusion, for the first time, of eleven potential curves and channel functions gives a groundstate energy that differs from the best variational calculation by 0.1 parts per million. The oscillator strength for the discrete helium transitions in the length-form and acceleration-form are also presented. We conclude that the HAA is no longer hampered by the lack of prescription for the obtainment of arbitrary precision wave functions for Coulombic systems.

A existência de seções globais para uxos é de central importância na teoria de sistemas dinâmicos, pois uma seção global simplica o estudo da dinâmica de um uxo reduzindo-o ao estudo da dinâmica de um difeomorsmo. Apresentamos detalhadamente a construção feita Hofer, Zehnder e Wysocki (em \'\'The dynamics on a strictly convex energy surface in R4\'\') de uma seção global para o uxo Hamiltoniano restrito a um nível de energia convexo em R4 . Uma importante consequência da existência dessa seção global é que o uxo Hamiltoniano restrito a um nível de energia convexo em R4 tem 2 ou innitas órbitas periódicas. Essa construção utiliza-se da teoria de curvas pseudo-holomorfas em simplectizações de variedades de contato desenvolvida pelos mesmos autores. Os argumentos apresentados também dão uma nova prova da Conjectura de Weinstein para formas de contato tight em S3 . / The existence of global surfaces of section to ows is of central importance in the theory of dynamical systems, as a global surface of section simplies the study of the dynamics of a ow reducing it to the study of the dynamics of a dieomorphism. We present in detail the construction due to Hofer, Wysocki and Zehnder (in \'\'The dynamics on a strictly convex energy surface in R4\'\') of a global surface of section for the Hamiltonian ow restricted to a convex energy level in R4 . An important consequence of the existence of the global surface of section is that the Hamiltonian ow restricted to a convex energy level in R4 has either 2 or innitely many periodic orbits. This construction makes use of the theory of pseudo-holomorphic curves in symplectizations of contact manifolds developed by the same authors. The arguments also give a new proof of Weinstein conjecture for tight contact forms in S3 .

Soluções não-adiabáticas em coordenadas hiperesférica para sistemas coulombianos de três corpos são apresentadas. Energias altamente precisas para o estado fundamental do hélio são obtidas, pela primeira vez, no método adiabática hiperesferico (HAA). Com a inclusão de somente três curvas de potencial e os correspondentes acoplamentos, precisão de partes por milhão foram obtidas. Concluímos que o HAA, usado exaustivamente para descrever semi-quantitativamente sistemas atômicos e moleculares, não está mais obstruído pela falata de prescrição para se obter funções de onda de precisão arbritária para sitemas coulombianos. / Non-adiabatic solutions for the Coulombic three-body systems in hyperspherical coordinates are presented. Highly accurated energies for the helium ground state are obtained, by the first time, in the hyperspherical adiabatic approach (HAA). With the inclusion of only three potential curves and the corresponding couplings, precision of parts per million have been achieved. We conclude that the HAA, exhaustively used to describe semi-quantitatively both molecular and atomic systems, is no longer more hampered by the lack of prescription for the obtainment of arbitrary precision wave functions for Coulombic systems.

A existência de seções globais para uxos é de central importância na teoria de sistemas dinâmicos, pois uma seção global simplica o estudo da dinâmica de um uxo reduzindo-o ao estudo da dinâmica de um difeomorsmo. Apresentamos detalhadamente a construção feita Hofer, Zehnder e Wysocki (em \'\'The dynamics on a strictly convex energy surface in R4\'\') de uma seção global para o uxo Hamiltoniano restrito a um nível de energia convexo em R4 . Uma importante consequência da existência dessa seção global é que o uxo Hamiltoniano restrito a um nível de energia convexo em R4 tem 2 ou innitas órbitas periódicas. Essa construção utiliza-se da teoria de curvas pseudo-holomorfas em simplectizações de variedades de contato desenvolvida pelos mesmos autores. Os argumentos apresentados também dão uma nova prova da Conjectura de Weinstein para formas de contato tight em S3 . / The existence of global surfaces of section to ows is of central importance in the theory of dynamical systems, as a global surface of section simplies the study of the dynamics of a ow reducing it to the study of the dynamics of a dieomorphism. We present in detail the construction due to Hofer, Wysocki and Zehnder (in \'\'The dynamics on a strictly convex energy surface in R4\'\') of a global surface of section for the Hamiltonian ow restricted to a convex energy level in R4 . An important consequence of the existence of the global surface of section is that the Hamiltonian ow restricted to a convex energy level in R4 has either 2 or innitely many periodic orbits. This construction makes use of the theory of pseudo-holomorphic curves in symplectizations of contact manifolds developed by the same authors. The arguments also give a new proof of Weinstein conjecture for tight contact forms in S3 .

The present thesis is devoted to two major atmospheric species – water and oxygen. The absorption spectrum of the 1Delta band of six oxygen isotopologues near was recorded by very high sensitivity CW-CRDS at room temperature and at 80 K. The magnetic dipole-allowed (0-0) band is observed for 16O2, 16O18O, 16O17O, 17O18O, 18O2 and 17O2. The first laboratory detection of extremely weak quadrupole transitions in the (0-0) band of 18O2, 16O17O, 17O2 is reported together with the (1-1) hot band of 16O2, 18O2, 16O17O and 17O2. The partly resolved hyperfine structure of the 16O17O, 17O18O, 17O2 transitions is analysed. These measurements combined with microwave and Raman data available in the literature led to the determination of the best to date spectroscopic constants for the six oxygen isotopologues, including the 17O hyperfine coupling parameters for the 1Delta state. The high resolution absorption spectra of water isotopologues (D216O, HD16O and H218O) were recorded by ICLAS and FTS in the 8800–14100 cm-1 region. The spectrum analysis based on high accuracy variational calculations provided a considerable amount of new energy levels for each of the isotopologues under consideration. The experimental energy levels derived in this study and available in the literature allowed calculating the line positions at the level of experimental accuracy in the 6100–15200 cm-1 region that extends much further the range of the present recordings. / Cette thèse est consacrée à deux espèces atmosphériques majeures: la vapeur d'eau et l'oxygène. Le spectre d'absorption de la bande 1Delta des six isotopologues de l'oxygène vers 1.27 micron a été enregistré à température ambiante et à 80 K par la technique CW-CRDS de très haute sensibilité. La bande (0-0) permise par le dipôle magnétique est observée pour les espèces 16O2, 16O18O, 16O17O, 17O18O, 18O2 et 17O2. La sensibilité expérimentale atteinte a permis de détecter pour la première fois au laboratoire (i) des transitions quadrupolaires électriques extrêmement faibles dans la bande (0-0) de 18O2, 16O17O et 17O2, (ii) la bande chaude (1-1) de 16O2, 18O2, 16O17O et 17O2 (iii) la structure hyperfine des transitions de 16O17O, 17O18O et 17O2. Ces mesures combinées avec des données micro-ondes et Raman disponibles dans la littérature ont permis de déterminer les meilleures constantes spectroscopiques à ce jour, y compris les paramètres de couplage hyperfin de 17O pour l'état 1Delta des six isotopologues de l'oxygène. Les spectres d'absorption à très haute résolution des isotopologues D216O, HD16O et H218O de la vapeur d'eau ont été enregistrés par ICLAS et FTS entre 8800 et 14100 cm-1. L'analyse du spectre basée sur les calculs variationnels de haute précision a fourni une quantité importante de nouveaux niveaux d'énergie pour chacun des isotopologues considérés. Les niveaux d'énergie expérimentaux obtenus dans cette étude et disponibles dans la littérature ont permis de calculer des positions de raies au niveau de la précision expérimentale dans la gamme 6100-15200 cm-1 qui s'étend bien au-delà de la gamme des enregistrements présents.

A new route to a well-defined block copolymer with alternating PEO-solubilising groups and fluorinated distyrylbenzene units was established. The Horner Wittig reaction was used as the polycondensation reaction. The non-fluorinated analogue of this block copolymer was prepared via the Wittig reaction. Both polymers were soluble in chloroform and free-standing films could be cast from solution. The position of the HOMO and LUMO energy levels of these two materials were determined by a combination of cyclic voltammetry, UV photoelectron spectroscopy and UV/Vis absorption spectroscopy. The presence of fluorine substituents on the distyrylbenzene unit had no influence on the HOMO-LUMO band-gap (3.0 eV). However, the position of these two energy levels relative to the vacuum level was shifted to higher energies (0.85 eV shift) in the case of the fluorinated block copolymer. The photoluminescence quantum efficiency of the fluorinated block copolymer was 17%, that of the non-fluorinated block copolymer was 34%. The former was used as the electron conducting layer in a light emitting diode with poly(p-phenylene vinylene) as the emissive layer. The latter was used as the emissive layer in light emitting diodes. Luminances over 2000 cd/m(^2) were observed for devices based on the non-fluorinated block copolymer using indium tin oxide as the anode and aluminium as the cathode. The luminescence efficiency of such devices was as high as 0.5 cd/A, corresponding to an internal quantum efficiency of 1.1%.Furthermore, an oligo(p-phenylene vinylene) was synthesised that contained two terminal fluorinated benzene rings and two central non-fluorinated benzene rings, all connected by vinylene bridges. This material aggregated in a 'brickwall' motif, where each molecule overlaps with two halves of molecules in the row above and below. The structure of this J aggregate is due to aryl-fluoroaryl-interactions and was demonstrated by X-ray crystal structure analysis.