Spectroscopic study of channel spectra phenomena in the synchrotron-based FTIR spectrometer at the Canadian Light Source

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Ibrahim, Amr
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy, c2010
Recently, the high radiance of synchrotron sources was used to enhance FTIR spectrometer performance. However, excessive channel spectra when synchrotron sources are used degrade the quality of retrieved spectral parameters. In the research reported in this thesis, seven different techniques for handling channel spectra were investigated. These techniques were used to reduce channel spectra for a test group of seven samples of CO2 mixed with air recorded using the synchrotron source at the Canadian Light Source. The increases in signal to noise ratio (SNR) of spectra handled with each technique were calculated. SNR results showed that transmission spectra, produced using synthetic background spectra with simulated channel spectra, achieved the highest SNR improvement. However, when the spectra groups were fitted using nonlinear least square fit algorithm, the technique using channel spectra fitting produced the smallest fitting residual. Moreover, the retrieved intensities and air broadening coefficients of 21 spectral lines showed that the spectral fitting technique produced the most accurate values as compared to the HITRAN 2008 database. Although the spectral fitting technique was accurate in retrieving spectral line parameters, applying the technique at wider spectral ranges was less accurate. A modification to the channel spectra fitting technique by performing iterations of channel fitting was introduced to process wider spectral ranges. Carbon dioxide laser band I centred at 961 wavenumber was analyzed using 24 spectra recorded under different experimental conditions. The intensity and air-and self-broadening coefficients were retrieved for 48 spectral lines with average deviations from HITRAN database values of 2.11%, 1.25% and 4.14%, respectively, using the Voigt profile. These average deviations lie within the uncertainty limits listed by the database. The deviation between our results and other results reported in the literature were also examined and it is found to be also within the range of HITRAN uncertainties. The effect of errors in fitting channel spectra parameters was examined and found to be mitigated by the inclusion of channel-free spectra in the multispectral fit.
xiv, 134 leaves : ill. ; 29 cm
Spectrum analysis , Greenhouse gases -- Research , Greenhouse effect, Atmospheric -- Research , Synchrotons , Fourier transform infrared spectroscopy , Remote sensing -- Research , Carbon dioxide -- Research , Canadian Light Source , LabVIEW , Dissertations, Academic