Date on Master's Thesis/Doctoral Dissertation

12-2019

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Chemistry

Degree Program

Chemistry, PhD

Committee Chair

Liu, Jinjun

Committee Co-Chair (if applicable)

Wittebort, Richard

Committee Member

Wittebort, Richard

Committee Member

Thompson, Lee

Committee Member

Mendes, Sergio

Author's Keywords

molecular spectroscopy; atmospheric chemistry; combustion chemistry; computational chemistry

Abstract

Understanding the mechanism of combustion reactions is key for advancing internal combustion engine design, improving the efficiency of ignition chemical reactions, and reducing pollutant formation. In order to model the extremely complicated chemical kinetics of combustion processes, it is critical to detect and identify transient reactive chemical intermediates, particularly free radicals. Hence, it needs to be fully understood the gas-phase chemistry of organic compounds in the lower atmosphere. Over the past fifty years, parallel advancement in observational, experimental, and theoretical techniques, tremendous strides have been made in our understanding of the role of organic compounds in the atmosphere. Combustion chemistry is extremely complex, partly because of the large number of reaction intermediates that are involved in the process. Here we propose laser spectroscopic investigations of oxygen-containing combustion intermediates such as alkoxy (ROˑ) and peroxy (ROOˑ) radicals. These investigations are aimed at elucidating the structures and dynamics of free radicals, which are generated by laser photolysis of judiciously chosen precursors in a flow cell and supersonic jet expansion. Spectroscopic interrogation of these species will be carried out using laser-induced fluorescence (LIF) spectroscopy, disperse fluorescence (DF), and cavity ring-down (CRD) spectroscopy. Vibrational structure of excited electronic states has been recorded using LIF and UV/visible/near-IR CRDS techniques, whereas DF and mid-IR CRDS techniques can be used to explore the vibrational structure of ground electronic states. Vibronic analyses were performed for the experimental spectra with the aid of quantum calculations. Accurate transition origin frequencies, excited and ground state vibrational frequencies, and Frank-Condon factors were determined for different intermediates such as isobutoxy, 2-methyl-1-butoxy, isopentoxy, 1-,2-,3-, and 4-methylcycholohexoy, and 1-,2-, and 3-methyl allyl peroxy.

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