Abstract

There is demonstrated need for the capability to detect spectral signatures of trace gases at atmospheric pressure. While many remote sensing techniques are effective, they suffer limitations in their ability to discriminate trace gases at high pressures. This stems from the broadening of spectral lines washing away the spectral fingerprint as pressure increases. A double-resonance (DR) infrared (IR)/Terahertz (THz) ro-vibrational spectroscopy solution is proposed. The ability to discriminate between molecules or specific isotopic isomers of the same molecule using this double-resonance spectroscopy (DRS) technique comes from the unique pump source coincidence with the spectral lines of the trace gas and the probing of the transient changes in absorption seen in neighboring rotational transitions. These pump/probe combinations are unique to each isotopic isomer. In order to predict the behavior of this technique at atmospheric pressures, it must first be understood in the low-pressure regime. A set of experiments were conducted using a pulsed carbon dioxide (CO2) long-wave infrared (LWIR) laser pump source and THz probe source. The trace gas interrogated was methyl chloride 35 (CH335Cl) and the diluting gas was nitrogen (N2). Hyperfine frequency contributions were measured, and transient coherent behavior was observed. A model was also developed to simulate the coherent behavior at low-pressures and predict what is expected in the atmospheric regime. Experimental methods and results are discussed along with model output and predictions and a path toward atmospheric DRS experiments is detailed.

Notes

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Graduation Date

2022

Semester

Fall

Advisor

Richardson, Martin

Degree

Master of Science (M.S.)

College

College of Optics and Photonics

Department

Optics and Photonics

Degree Program

Optics and Photonics

Format

application/pdf

Identifier

CFE0009408; DP0027131

URL

https://purls.library.ucf.edu/go/DP0027131

Language

English

Release Date

December 2027

Length of Campus-only Access

5 years

Access Status

Masters Thesis (Campus-only Access)

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