An infrared active polyatomic molecule has several vibrational modes, each of which has a characteristic frequency. If the molecule is trapped in a matrix of perturbing atoms, those vibrational frequencies will shift, and if the vibrational mode is degenerate, the perturbation may lift the degeneracy. Such shifts and splitting are due to the dependence of the chromophore/matrix-atom interaction potential on the internal vibrational motion of the chromophore. Applying a previously-developed model for the shifting and splitting of the triply degenerate <em>&nu;</em>₃ mode of SF₆ perturbed by a rare gas atom, we use Monte Carlo simulations to sample the accessible equilibrium configurations of the system and to predict the associated thermally averaged perturbed IR spectra. Since the experimental spectrum has 10 peaks while the triply degenerate <em>&nu;</em>₃ mode of SF₆ in a particular environment could have at most 3 peaks, the observed spectrum must be a combination of spectra for SF₆ trapped in different types of lattice sites. A fit to experiment of simulated spectra generated from a family of lattice sites is then used to identify the peaks in the experimental spectrum, determine the relative importance of the various lattice sites, and semi-quantitatively reproduce the experimental spectrum.

An infrared active polyatomic molecule has several vibrational modes, each of which has a characteristic frequency. If the molecule is trapped in a matrix of perturbing atoms, those vibrational frequencies will shift, and if the vibrational mode is degenerate, the perturbation may lift the degeneracy. Such shifts and splitting are due to the dependence of the chromophore/matrix-atom interaction potential on the internal vibrational motion of the chromophore. Applying a previously-developed model for the shifting and splitting of the triply degenerate <em>&nu;</em>₃ mode of SF₆ perturbed by a rare gas atom, we use Monte Carlo simulations to sample the accessible equilibrium configurations of the system and to predict the associated thermally averaged perturbed IR spectra. Since the experimental spectrum has 10 peaks while the triply degenerate <em>&nu;</em>₃ mode of SF₆ in a particular environment could have at most 3 peaks, the observed spectrum must be a combination of spectra for SF₆ trapped in different types of lattice sites. A fit to experiment of simulated spectra generated from a family of lattice sites is then used to identify the peaks in the experimental spectrum, determine the relative importance of the various lattice sites, and semi-quantitatively reproduce the experimental spectrum.

This study addresses the structure and the bonding in the family of tetrahedral boranes. The specific molecules studied are the series B4X4 (X=H, F, Br, Cl, I), the series B4BrCl3, B4Br2Cl2, and B4Br3Cl and tetra-tert-butyl-tetraborane, t-Bu4B4. The research presented herein employs the Hartree-Fock Self Consistent Field (HFSCF), the Moller-Plesset second-order perturbation theory (MP2), and the Density Function Theory (DFT). A variety of basis sets was employed. Our calculations are the first theoretical studies of B4Br4, B4I4, B4BrCl3, B4Br2Cl2, and B4Br3Cl, and are also the first calculations for the D4h structures of any of these molecules, except for B4H4. These results were compared with experimental results, where such comparisons can be made. The most energetically stable structure for all the B4X4 and B4BrnClm molecules has symmetry Td.

Laser diagnostics are fast-response, non-intrusive and species-specific tools perfectly applicable for studying combustion processes. Quantitative measurements of species concentration and temperature require spectroscopic data to be well-known at combustion-relevant conditions. Absorption cross-section is an important spectroscopic quantity and has direct relation to the species concentration. In this work, the absorption cross-sections of basic hydrocarbons are measured using Fourier Transform Infrared (FTIR) spectrometer, tunable Difference Frequency Generation laser and fixed wavelength helium-neon laser. The studied species are methane, methanol, acetylene, ethylene, ethane, ethanol, propylene, propane, 1-butene, n-butane, n-pentane, n-hexane, and n-heptane. The Fourier Transform Infrared (FTIR) spectrometer is used for the measurements of the absorption cross-sections and the integrated band intensities of the 13 hydrocarbons. The spectral region of the spectra is 2800 – 3400 cm-1 (2.9 – 3.6 μm) and the temperature range is 673 – 1100 K. These valuable data provide huge opportunities to select interference-free wavelengths for measuring time-histories of a specific species in a shock tube or other combustion systems. Such measurements can allow developing/improving chemical kinetics mechanisms by experimentally determining reaction rates. The Difference Frequency Generation (DFG) laser is a narrow line-width, tunable laser in the 3.35 – 3.53 μm wavelength region which contains strong absorption features for most hydrocarbons due to the fundamental C-H vibrating stretch. The absorption cross-sections of propylene are measured at seven different wavelengths using the DFG laser. The temperature range is 296 – 460 K which is reached using a Reflex Cell. The DFG laser is very attractive for kinetic studies in the shock tube because of its fast time response and the potential possibility of making species-specific measurements. The Fixed wavelength helium-neon (HeNe) laser at 3.39 μm is used to measure the absorption cross-section of the fuels mentioned above. The dependence on temperature, pressure and bath gas (helium, argon and nitrogen) is also examined. The temperature and pressure ranges of this study are 296 – 800 K and 250 – 1000 Torr, respectively. These are the first measured cross-sections at HeNe laser wavelength that are applicable at combustion-relevant conditions.

No description available.

Le présent travail de thèse a porté sur l’étude expérimentale et théorique de signatures spectroscopiques de molécules atmosphériques clés: CO2 et CH3D. 11 a été divise en partie expérimentale, consacrée aux mesures a haute pression des spectres IR CO2, et a la partie théorique, a. savoir le calcul des largeurs de ligne de collision pour CH3D perturbé par divers gaz. Dans la première partie, j'ai présenté des mesures &absorption de CO2 a haute pression a température ambiance dans l'intervalle spectral 600-9650 cm (sondes dans des études d’atmosphère planétaire) pour deux raisons principales: fournit des données exactes et étendues et suivre l’évolution de effets de "line-mixing" avec des variations graduelles de pression. Dans la deuxième partie, j'ai présenté des calculs semi-classiques des coefficients d'élargissement de CH3D -N2 (-H2) en utilisant le modèle de trajectoire exacte dans les bandes v3 parallèles et perpendiculaires vs, v6 de CH3D ---N2 ainsi que dans la bande v3 parallèle de CH3D -142 pour de grands intervalles les de nombres quantiques de rotation requis pour les bases de données spectroscopiques. / Present Ph.D work has focused on experimental and theoretical studying of spectroscopic signatures of key atmospheric molecules: CO2 and CH3D. It was divided into experimental part, devoted to high-pressure measurements of IR CO2 spectra, and theoretical part, namely calculation of collisional line-widths for CH3D perturbed by various gases. In the first part, I reported room-temperature high-pressure CO2 absorption measurements in the spectral interval 600-9650 cm-1 (probed in planetary atmosphere studies) with the double goals: to provide accurate and extensive data and to trace evolution of the line-mixing effects with gradual pressure variations. In the second part, I presented semi-classical calculations of CH3D-N2 and -142 line-broadening coefficients using exact trajectory model in the parallel v3 and perpendicular vs, v6 bands of CH3D-N2 as well as in the parallel v3 band of CH3D-112 for large intervals of rotational quantum numbers required for spectroscopic databases.

Σε αυτή την εργασία περιγράφονται οι αντιδράσεις αλάτων του κοβαλτίου(ΙΙ) [Co(O2CMe)2•4H2O, Co(ClO4)2•6H2O και Co(O2CPh)2] με την Ν-σαλικυλιδενο-4- μεθυλο-ο-αμινοφαινόλη (saphΗ2-4Me), την Ν-σαλικυλιδενο-4-χλωρο-ο-αμινοφαινόλη (saphΗ2-4Cl) και την Ν-σαλικυλιδενο-ο-αμινοφαινόλη (saphΗ2). Από τo σύστημα αντίδρασης Co(O2CMe)2•4H2O/saphΗ2-4Me/ΝaΟΗ σε διαλύτη MeOH απομονώθηκε ένα οκταεδρικό σύμπλοκο με τύπο (Η5Ο2)[CoΙΙΙ(saph-4Me)2]•H2O (1). Χρησιμοποιώντας την Εt3N ως βάση, από ένα ανάλογο σύστημα αντίδρασης, απομονώθηκε ένα οκταεδρικό σύμπλοκο με τύπο (Εt3NH)[CoΙΙΙ(saph-4Me)2]•ΜeCΟ2Η•MeOH (2). Από το σύστημα αντίδρασηςfCo(O2CMe)2•4H2O/ saphΗ2-4Cl/Εt3N σε διαλύτη MeOH απομονώθηκε το ισοδομικό του συμπλόκου 2, δηλαδή το σύμπλοκο (Εt3NH)[CoΙΙΙ(saph-4Cl)2]•ΜeCΟ2Η•MeOH (3). Οι τρεις σύμπλοκες ενώσεις χαρακτηρίστηκαν με IR φασματοσκοπία, ενώ για τα σύμπλοκα 1 και 2 πραγματοποιήθηκαν και μετρήσεις 1Η ΝΜR φασματοσκοπίας. Οι κρυσταλλικές δομές των συμπλόκων 1, 2 και 3 επιλύθηκαν με κρυσταλλογραφία ακτίνων Χ μονοκρυστάλλου. Βάσει των πειραματικών δεδομένων και τα τρία σύμπλοκα είναι ανιοντικά μονοπυρηνικά με το ιόν του κοβαλτίου(ΙΙΙ) να περιβάλλεται από δύο τριδοντικούς, πλήρως αποπρωτονιωμένους, υποκαταστάτες, οι οποίοι ενώνονται με αυτό μέσω των δύο αποπρωτονιομένων φαινολικών οξυγόνων και με το άτομο του ιμινικού αζώτου. Τα κατιόντα είναι το Η5Ο2+ για το σύμπλοκο 1 και το Εt3NH+ για τα 2 και 3. / In this work the reactions of cobalt(II) salts [Co(O2CMe)2•4H2O, Co(ClO4)2•6H2O and Co(O2CPh)2] with N-salicylidene-4-methyl-o-aminophenol (saphH2-4Me), N-salicylidene-4-chloro-o-aminophenol (saphH2-4Cl) and N-salicylidene-o-aminophenol (saphH2) Schiff bases are described. From the Co(O2CMe)2•4H2O/ saphH2-4Me/NaOH reaction system in MeOH we have isolated a six-coordinated complex with the formula (H5O2)[CoΙΙΙ(saph-4Me)2]•H2O (1). From a similar reaction system with Et3N as a base, we isolated a six-coordinated complex with the formula (Et3NH)[CoΙΙΙ(saph-4Me)2]•MeCO2H•MeOH (2). The Co(O2CMe)2•4H2O/saphH2-4Cl/Et3N reaction system in MeOH has led to the complex (Et3NH)[CoΙΙΙ(saph-4Cl)2]•MeCO2H•MeOH (3), which is isostructural to 2. The three complexes have been characterized by IR spectroscopy, while the complexes 1 and 2 have been also studied by 1H NMR spectroscopy. The crystal structures of 1, 2 and 3 have been determined by single-crystal X-ray crystallography. Based on experimental results, all the three complexes are anionic mononuclear with the CoIII ion being surrounded by two tridentate dianionic Schiff-base ligands, which chelate the metal ion through the deprotonated phenolic oxygen atoms and the nitrogen atom of the azomethine group. The cation for the complex 1 is H5O2+, while for the complexes 2 and 3 the cation is Et3NH+.