Doctoral Dissertations

Date of Award

12-2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Physics

Major Professor

Christian G. Parigger

Committee Members

Reza Abedi, Marianne Breinig, Steve Johnston

Abstract

This dissertation focuses on laser-induced plasma of diatomic molecular cyanide. Optical breakdown plasma generation is produced by high-peak-power 1064 nm Q-switched nanosecond pulsed radiation. Laser-induced breakdown is performed on a 1:1 molar gas mixture of carbon dioxide and nitrogen held at a fixed pressure of 760 Torr, a 1:1 molar gas mixture of carbon dioxide and nitrogen held at a fixed pressure of 2069 Torr, and a flowing 1:1 molar gas mixture of carbon dioxide and nitrogen flowing at a rate of 100 mL per minute. Plasma shockwave measurements in laboratory air are shown to determine the shock front geometry and confirm the shockwave dynamics in the carbon dioxide and nitrogen gaseous mixtures are similar to that of air. Of specific interest are the effects of the shockwave on the cyanide plasma distribution at early time delays. Analysis of line-of-sight measurements determine the excitation temperatures and electron densities. Specifically, atomic carbon spectra show increased electron densities near the shockwave, which are determined by inferred Stark widths and Stark shifts of an atomic carbon line overlapping with the cyanide violet band heads. Fitting of measured diatomic molecular cyanide spectra to theoretically produced cyanide spectra allow for the determination of excitation temperatures, which showed higher excitation temperatures near the shockwave. Lastly, inferences of the spatiotemporal plasma distribution are performed using integral inversion techniques.

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