Laser Spectroscopy of Hydrocarbons for Applications in Atmospheric and Space Science

Author: Ober, Douglas Clifford

Year: 2023

Degree: Dissertation (Ph.D.)

Advisor: Okumura, Mitchio

Committee Members: Blake, Geoffrey A.; Okumura, Mitchio; Beauchamp, Jesse L.; Hodyss, Robert P.; Cushing, Scott K.

Option: Chemistry

DOI: 10.7907/x42v-ry39

Abstract

This thesis describes applications of spectroscopy and mass spectrometry towards applications of in situ sensing, chemical kinetics, and photodissociation processes of hydrocarbon species. Both mass spectrometry and cavity ring-down spectroscopy are used in this work. Irradiation of protonated coronene was used to study photodissociation process of polycyclic aromatic hydrocarbons (PAHs), with the power, irradiation time, and fragmentation studied to elucidate a photofragmentation mechanism. Biomolecules were ionized via Direct Analysis in Real Time (DART) to explore the feasibility and sensitivity of the ionization technique for different chemical species for in situ measurement in simulated extraterrestrial conditions. Photofragmentation and DART ionization were combined to quantify mixtures of isobaric PAHs, providing a tunable and complimentary technique for in situ analysis of mixtures. Finally, frequency-stabilized cavity ring-down spectroscopy was used to analyze precise ¹³CH₄, CH₃D, and CH₂D₂ to CH₄ isotologue ratios using optically-switched dual-wavelengths, allowing for sensitive measurement of the kinetic isotope effect of methane oxidation with O(¹D).

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