This thesis describes the application of far-infrared and mid-infrared, laboratory based, high-resolution laser spectroscopy to the measurement of line profiles of atmospherically relevant molecules. Such data is invaluable in the retrieval of concentration profiles from remote sensing data. Chapter one contains an overview of the far-infrared and mid-infrared regions of the electromagnetic spectrum and highlights the need to develop high power, high efficiency, tunable, coherent radiation sources. Some of the more promising technologies are outlined together with some potential applications. The experimental details concerning the operation of a tunable far-infrared spectrometer, based on non-linear mixing and a mid-infrared spectrometer based on tunable lead-salt diode lasers, are then given in Chapter 2. Theoretical aspects of line broadening are considered in Chapter 3 and a protocol is developed for the retrieval of pressure broadening data. The validity of the protocol is demonstrated by critically examining three well studied and atmospherically important molecules: H<sup>35</sup>Cl, SO<sub>2</sub> and N<sub>2</sub>O. Chapter 4 and Chapter 5 examine the nitrogen, oxygen and self broadening of methyl iodide and methyl bromide respectively. Measurements of pressure broadening coefficients were obtained, for the first time, in the <i>v</i><sub>5</sub> perpendicular bands of both molecules. The lines from five <i>Q</i> branches formed the bulk of the study for each molecule, with some <i>P</i> and <i>R</i> branch lines also being examined. Primarily, the <i>J</i> dependence of the broadening coefficients was obtained but some knowledge of the <i>K</i> dependence was also gleaned. Finally, in Chapter 6, some recommendations for the development of the spectrometer are made and some suggestions for potential target molecules, that could form the basis of a future study, are given.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:604138 |
| Date | January 2010 |
| Creators | Hoffman, K. J. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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