Spectroscopic study of methane in the v1 + v4 band broadened by itself, air and hydrogen

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Arifuzzaman, Md
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : Universtiy of Lethbridge, Department of Physics and Astronomy
This thesis presents the temperature-dependent line-shape studies of methane broadened by itself, air and hydrogen, which is identified as the second most important anthropogenic greenhouse gas in the Earth’s atmosphere due to its high global warming potential. A set of 14 laboratory spectra of pure methane and lean mixtures of methane in air were recorded over a range of temperatures from 148.4 to 298.4 K and total sample pressures from 4.5 to 385 Torr using a high-resolution Fourier Transform Spectrometer (FTS) at the Jet Propulsion Laboratory (JPL), California. A coolable absorption gas cell with the optical path length 20.38 cm was used in the recording of methane-air spectra. A non-linear least-squares multi-spectrum fitting program called ‘Labfit’ was used to determine the Lorentz half-width, pressure-induced shift coefficients along with their temperature dependences, speed-dependence parameters and line-mixing coefficients due to self- and air-broadening of methane in its strongest band v1 + v4. A set of 18 laboratory spectra of methane broadened by itself and hydrogen were also recorded at various temperatures (148.4-298.4 K) and pressures (0.12-385 Torr) using an FTS at JPL. Various line-shape parameters such as line positions, intensities, self- and air-broadened line widths and pressure-induced shifts along with their temperature dependences are reported in the v1 + v4 band of methane. A Speed-Dependent Voigt Profile (SDVP) was implemented in the retrieval of line parameters in both cases. The linemixing coefficients were quantified using the off-diagonal relaxation matrix element formalism. The off-diagonal relaxation-matrix coefficients were determined due to self-, air- and H2-broadening of methane using Labfit program.
Methane -- Spectra -- Research , Atmospheric methane -- Research , Molecular spectroscopy , Spectral line broadening , Greenhouse gases -- Research , methane broadening , methane spectra , methane spectroscopic studies , temperature dependent line shape studies , Dissertations, Academic