Graduation Year

2025

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Physics

Major Professor

Andreas Muller, Ph.D.

Committee Member

Dario Arena, Ph.D.

Committee Member

Humberto Rodríguez Gutiérrez, Ph.D.

Committee Member

John Kuhn, Ph.D.

Keywords

trace gas sensing, optical cavity, non-resonant

Abstract

The recent development of Raman spectroscopy as a powerful analytical tool for trace gas analysis owes much to not only advancements in modern optoelectronic tools but also to substantial research in enhancement techniques. Feedback-assisted, non-resonant, multipass cavity Raman spectroscopy stands out among various Raman enhancement methods. We effectively employed this technique to estimate the deuterium/hydrogen ratio in water vapor, to simultaneously identify and quantify multiple analytes, even at extremely low concentrations such as 20 parts-per-billion for methane (CH4), and to detect hydrogen (H2) at concentrations as low as 75 parts-per-billion. This dissertation focuses on the practical application of spontaneous Raman scattering to study the insulating gas 2,3,3,3-tetrafluoro-2-(trifluoromethyl) propanenitrile (C4F7N), used in gas-insulated switchgear. Notably, this is the first time its Raman spectrum has been investigated. When subjected to arcing, C4F7N undergoes decomposition, producing a variety of by-product gases at a wide range of concentrations, posing challenges for monitoring. We compared our Raman scattering results with gas chromatography-mass spectrometry and found that Raman scattering not only detected these by-product gases as gas chromatography-mass spectrometry did, but also identified additional gases, such as carbon monoxide (CO), methane (CH4), and hydrogen (H2), which were undetected by gas chromatography-mass spectrometry or require a separate detector system, at concentrations as low as 10 parts-per-million. Although gas chromatography-mass spectrometry offers high selectivity, the results from spontaneous Raman scattering demonstrate that it is an equally efficient detection system, if not better. Raman scattering paves the way for portable trace gas sensors, offering the potential to revolutionize field-deployed trace gas detection systems.

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