## High resolution spectroscopic study of atmospheric trace gases with climate research application

2018
##### Authors
Hashemi, Robab
University of Lethbridge. Faculty of Arts and Science
##### Publisher
Lethbridge, Alta. : Universtiy of Lethbridge, Department of Physics and Astronomy
##### Abstract
The presented research was conducted to collect, and analyze the laboratory spectroscopic data together with theoretical calculations of the line shape parameters for the HITRAN (High Resolution Transmission) molecular spectroscopic database. The most updated version of this database is HITRAN2016 \cite{HITRAN16}, and this research has contributed to this database by adding improved laboratory results to it. There is a demand for accurate retrieval of concentration values for carbon dioxide and methane (with accuracy better than 0.3 percent) which requires accurate line shape parameters. These line shape parameters are invaluable for modelling and interpreting spectra of Earth and planetary atmospheres. It is necessary to measure advanced line shape parameters such as the speed-dependence (to explain the impact of the speed of colliding molecules) and line mixing (where there is interference of neighbouring transitions) for all the transitions in the databases. The molecules of interest for the present research are atmospheric trace gases; acetylene (C$_2$H$_2$), methane (CH$_4$) and carbon monoxide (CO). For C$_2$H$_2$, the goal is to determine the fundamental Boltzmann constant based on a line shape analysis of $\nu_1+\nu_3$ band recorded using a tunable diode laser. The next focus of the thesis is the examination of different line profiles on the absorption spectra of the CO-CO$_2$ in the $2-0$ band and CH$_4$-air in 2.3 $\mu m$. A standard multispectrum non-linear least squares fitting technique is used to measure line width and line shift coefficients, and their temperature dependencies considering the effect of speed dependence and line mixing.
##### Keywords
Spectrum analysis , Methane -- Spectra , Acetylene -- Sprectra , Carbon monoxide -- Spectra , High resolution spectroscopy , Remote sensing , Dissertations, Academic , line shape study , speed dependent effect , Voigt profile