Spectroscopic study of methane in the v1 + v4 band broadened by itself, air and hydrogen
Date
2018
Authors
Arifuzzaman, Md
University of Lethbridge. Faculty of Arts and Science
Journal Title
Journal ISSN
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Publisher
Lethbridge, Alta. : Universtiy of Lethbridge, Department of Physics and Astronomy
Abstract
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.
Description
Keywords
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