Department or Program

Physics and Astronomy

Abstract

Methane (CH4) is one of the major greenhouse gases. Although its atmospheric abundance is lower than that of carbon dioxide (CO2), it contributes significantly to current global warming and exhibits a stronger warming effect on short-term timescales. Because methane has a relatively short atmospheric lifetime, obtaining high-quality, comparable, and traceable methane measurement data is crucial for emission monitoring, source attribution, and the evaluation of mitigation actions. This thesis focuses on near-infrared methane absorption spectroscopy measurements, aiming to establish a foundational framework from experimental platforms to data analysis inputs, thereby laying the groundwork for subsequent, more systematic and precise spectral analysis. This thesis first introduces the theoretical background underlying methane absorption spectroscopy, including molecular absorption, spectral line broadening mechanisms, and frequency references. Subsequently, an experimental setup for near-infrared methane measurements was constructed, comprising a DFB semiconductor laser operating at approximately 1645 nm, a short-path methane absorption cell, detection and reference channels, and an oscilloscope-based digital data acquisition system, designed to collect absorption spectral data for 12CH4 and 13CH4 under various pressure conditions. Regarding data processing, this thesis establishes a comprehensive data acquisition and processing workflow, where raw experimental signals undergo frequency calibration, spectral reduction, spectral alignment, and ultimately being organized into standardized analytical inputs. In the validation section, consistency checks of the processed spectra were performed using Allan deviation analysis. Overall, this thesis has established an experimental and analytical framework for high-resolution near-infrared absorption measurements of methane, providing the experimental foundation and methodological preparation for subsequent, more reliable full fitting and precise spectral parameter extraction.

Level of Access

Open Access

First Advisor

Cole, Ryan

Date of Graduation

5-2026

Degree Name

Bachelor of Science

Number of Pages

88

Components of Thesis

1 pdf file

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