Spectroscopic investigation of molecules relevant to Titan's atmosphere and combustion processes
Abstract
The work discussed in this text involves the vibronic spectroscopy of nitrile and isonitrile compounds related to Titan’s atmosphere and the vibronic and infrared spectroscopy of alkyl radicals formed in the initial stages in combustion. The Titan molecules are important precursors as possible vehicles for nitrogen incorporation into larger biologically relevant core molecules. The combustion radicals are modelled as an initial step in combustion, and their characterization helps to refine the models used for combustion reactions and products. All of the experiments discussed in this work are jet-cooled to the zero-point vibronic level to simplify the spectra. Double-resonance methods were used extensively to identify-conformation-specific features for the molecules studied. Selections of computational methods were also used to aid in the analysis of experimental spectra. Titan has a nitrogen atmosphere containing trace hyrdrocarbons and nitrogenated compounds. The temperatures and pressures in the upper atmosphere of Titan make the cooling methods used an effective laboratory model for the conditions where reactions could occur. As a result, our investigations of isonitriles and nitrogenated compounds enable us to make conclusions about the plausibility of proposed reactive pathways. Further, we specifically seek out quinoline isomers as precursors to these important prebiotic molecules. Thusly, para-isocyanobenzonitrile is investigated as a part of an isoelectronic series to understand nitrile-isonitrile isomerization processes and the possibility for nitrogen incorporation into larger systems. The characterizations of ortho-, meta-, and para-cyanostyrene were performed as isomers and plausible precursors to isoquinoline. The alkyl radicals discussed were generated in electrical discharge in a preexpansion prior to final cooling. The alkyl benzyl radicals were studied to understand combustion processes. An additional investigation in the alkyl benzyl radical project involved comparing experimental work to a collaborator’s local mode model for infrared spectroscopy to account for stretch-bend Fermi resonance in the alkyl CH stretch region. This thesis presents the first example of double-resonance spectroscopy to identify multiple conformers on a radical system.
Degree
Ph.D.
Advisors
Zwier, Purdue University.
Subject Area
Chemistry|Physical chemistry
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