Résumé : Ce travail avait pour but de contribuer à la détermination précise des paramètres de raies du disulfure de carbone en vue d'applications atmosphériques. Il s'agissait de déterminer théoriquement et expérimentalement les coefficients d'élargissement collisionnel de raies de la bande gamma 3 du disulfure de carbone perturbé par l'air atmosphérique ainsi que leur dépendance en température. Pour cela, nous avons déterminé les coefficients d'élargissement collisionnel du disulfure de carbone perturbé par l'azote, l'oxygène et enfin par l'argon, principaux composants de l'air atmosphérique, aussi bien que leur dépendance en température. En outre, nous avons déterminé théoriquement et expérimentalement les coefficients d'auto élargissement collisionnel de raies de la bande gamma 3 - gamma 1 du disulfure de carbone, à température ambiante. La dépendance vibrationnelle des largeurs collisionnelles étant négligeable, les résultats sont valables quel que soit le niveau supérieur de la transition. Enfin, nous avons déterminé les intensités absolues de quelques raies de la bande gamma 3 - gamma 1 du disulfure de carbone qui nous ont permis de mettre en exergue une des applications atmosphériques des paramètres de raie mesurés en laboratoire. Pour la partie expérimentale, un spectromètre diode-laser haute résolution (5x10-4cm-1) a été utilisé pour enregistrer les différents spectres. De ces derniers, nous avons déterminé les différents paramètres de raie d'absorption en ajustant aux profils expérimentaux des modèles de profils théoriques. Du point de vue théorique, les différents coefficients d'élargissement collisionnel ont été calculés sur base du formalisme semi-classique d'Anderson-Tsao-Curnutte amélioré par J. Bonamy et D. Robert, moyennant quelques modifications pour accorder les valeurs à celles mesurées en laboratoire. Ceci a permis de valider les différents potentiels d'interaction pour les différents systèmes moléculaires considérés. Abstract The purpose of this thesis was to contribute to the accurate determination of line parameters of carbon disulfide for atmospheric applications. We have determined experimentally as well as theoretically the collisional broadening coefficients of lines in the gamma 3 band of carbon disulfide perturbed by the atmospheric air and their temperature dependence. To this end, we determined collisional broadening coefficients, as well as their temperature dependence, of carbon disulfide diluted in nitrogen, oxygen and argon; the main components of the atmospheric air. In addition, we determined the self broadening coefficients of lines in the gamma 3 - gamma 1 band of carbon disulfide at room temperature. As the vibrational dependence of collisional widths is negligible, our results are valid whatever the higher level of transition. Finally, we determined the absolute intensities of a few lines in the gamma 3 - gamma 1 band of carbon disulfide, which have enabled us to highlight one of the atmospheric applications of line parameters measured in the laboratory. For the experimental part, a high resolution diode-laser spectrometer (5x10-4cm-1) was used to record the different spectra. Of these, we determined the parameters of absorption line by adjusting theoretical lineshape models to experimental profiles. From a theoretical point of view, different collisional broadening coefficients were calculated on the basis of semi classical formalism of Anderson-Tsao-Curnutte improved by J. Bonamy and D. Robert, with some modifications to make the calculated values more consistent with those measured. This enabled us to validate the different potentials of interactions for the different molecular systems considered.

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<p dir="ltr">Transitioning to a carbon-neutral future will require a broad portfolio of green energy generation and storage solutions. With the abundant availability of solar radiation across the Earth’s surface, energy generation from photovoltaics (PVs) will be an important part of this green energy portfolio. While silicon-based solar cells currently dominate the PV market, temperatures exceeding 1000 °C are needed for purification of silicon, and batch processing of silicon wafers limits how rapidly Si-based PV can be deployed. Furthermore, silicon’s indirect band gap necessitates absorber layers to exceed 100 µm thick, limiting its applications to rigid substrates.</p><p dir="ltr">Solution processed thin-film solar cells may allow for the realization of continuous, high-throughput manufacturing of PV modules. Thin-film absorber materials have direct band gaps, allowing them to absorb light more efficiently, and thus, they can be as thin as a few hundred nanometers and can be deposited on flexible substrates. Solution deposition of these absorber materials utilizing molecular precursor-based inks could be done in a roll-to-roll format, drastically increasing the throughput of PV manufacturing, and reducing installation costs. In this dissertation, solution processed synthesis and the characterization of two emerging direct band gap absorber materials consisting of earth abundant elements is discussed: the enargite phase of Cu₃AsS₄ and the distorted perovskite phase of BaZrS₃.</p><p dir="ltr">The enargite phase of Cu₃AsS₄ (ENG) is an emerging PV material with a 1.42 eV band gap, making it an ideal single-junction absorber material for photovoltaic applications. Unfortunately, ENG-based PV devices have historically been shown to have low power conversion efficiencies, potentially due to defects in the material. A combined computational and experimental study was completed where DFT-based calculations from collaborators were used inform synthesis strategies to improve the defect properties of ENG utilizing new synthesis techniques, including silver alloying, to reduce the density of harmful defects.</p><p dir="ltr">Chalcogenide perovskites are viewed as a stable alternative to halide perovskites, with BaZrS₃ being the most widely studied. With a band gap of 1.8 eV, BaZrS₃ could be an excellent wide-bandgap partner for a silicon-based tandem solar cell.Historically, sputtering, and solid-state approaches have been used to synthesize chalcogenide perovskites, but these methods require synthesis temperatures exceeding 800 °C, making them incompatible with the glass substrates and rear-contact layers required to create a PV device. In this dissertation, these high synthesis temperatures are bypassed through the development of a solution-processed deposition technique.A unique chemistry was developed to create fully soluble molecular precursor inks consisting of alkaline earth metal dithiocarboxylates and transition metal dithiocarbamates for direct-to-substrate synthesis of BaZrS₃ and BaHfS₃ at temperatures below 600 °C.</p><p dir="ltr">However, many challenges must be overcome before chalcogenide perovskites can be used for the creation of photovoltaic devices including oxide and Ruddlesden-Popper secondary phases, isolated grain growth, and deep level defects. Nevertheless, the development of a moderate temperature solution-based synthesis route makes chalcogenide perovskite research accessible to labs which do not have high temperature furnaces or sputtering equipment, further increasing research interest in this quickly developing absorber material.</p>

In this work, experimental and theoretical approaches are applied to the study of chemical reaction dynamics. In Chapter 2, two applications of transition state theory are presented: (1) Application of microcanonical transition state theory to determine the rate constant of dissociation of C2F3I after π∗ ← π excitation. It was found that this reaction has a very fast rate constant and thus is a promising system for testing the statistical assumption of molecular reaction dynamics. (2) A general rate constant expression for the reaction of atoms and molecules at surfaces was derived within the statistical framework of flexible transition state theory. In Chapter 4, a computationally efficient TDDFT approach was found to produce useful potential energy surface landscapes for application to non-adiabatic predissociative dynamics of the molecule CS2 after excitation from the ground state to the singlet C-state. In Chapter 5, ultrafast experimental results of excitation of CS2 to the predissociative neutral singlet C-state is presented. The bandwidth of the excitation laser was carefully tuned to span a two-component scattering resonance with each component differently evolving electronically with respect to excited state character during the quasi-bound oscillation. Scalar time-resolved photoelectron spectra (TRPES) and vector time-resolved photoelectron angular distribution (TRPAD) observables were recorded during the predissociation. The TRPES yield of photoelectrons was found to oscillate with a quantum beat pattern for the photoelectrons corresponding to ionization to the vibrationless cation ground state; this beat pattern was obscured for photoelectron energies corresponding to ionization from the vibrationally excited CS2 cation. The TRPAD data was recorded for two general molecular ensemble cases: with and without a pre-excitation alignment laser pulse. It was found that in the case of ensemble alignment (Chapter 6), the “molecular frame” TRPAD (i.e. TRMFPAD) was able to image the purely valence electronic dynamics of the evolving CS2 C-state. The unaligned ensemble TRPAD observable suffers from excessive orientational averaging and was unable to observe the quantum beat. Engineering efforts were also undertaken to eliminate scattered light background signal (Chapter 7, Appendix A) and improve laser stability as a function of ambient pressure (Appendix B) for TRMFPAD experiments. / Thesis (Ph.D, Chemistry) -- Queen's University, 2012-09-11 22:18:20.89