Kendall, Paul Anthony; (2003) Spectroscopic studies of atmospheric molecules related to global warming. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis presents the results of spectroscopic studies performed on a number of atmospheric molecules related to global warming. The studies have been performed using electron impact and photoabsorption spectroscopy and the results have been compared, where possible, with previous work. The molecules studied were trifluoromethyl sulphur pentafluoride (SF5CT3), trifluoromethyl iodide (CF3I), ozone (O3) and acetonitrile (CH3CN). The first two molecules are entirely anthropogenic and may have potentially serious effects upon global warming and ozone depletion respectively. Atmospheric lifetimes and global warming potentials have been calculated for both molecules. The first temperature-dependent infrared measurements of SF5CF3 suggest it is a more effective global warming agent than first thought. Measurements of the destruction of condensed phase ozone by electrons may provide valuable information for modelling atmospheric destruction of ozone upon the surfaces of polar stratospheric clouds (PSCs). Acetonitrile is a by-product of biomass burning and may. In the future, allow remote detection and tracking of biomass burning. Photoabsorption measurements have been used to calculate the lifetime of the molecule in the atmosphere and, combined with temperature dependent infrared measurements, to estimate the global warming potential of the molecule. The thesis consists of nine chapters. The first is an introduction to the thesis and covers both modem spectroscopy and the structure of the atmosphere. The second chapter discusses molecular spectroscopy and the measured quantities in photoabsorption and electron-impact experiments. The third chapter describes the various apparatus used to obtain the experimental results. The fourth chapter describes some computer programs that have been developed to analyse the experimental data. Chapters five to eight present the experimental results which are compared, where available, with previous data. The results obtained using the computer models are also presented in these chapters. chapter nine concludes the thesis, summarises the results and makes suggestions for future work.

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