Ultraviolet photodissociation of atmospheric halogen sources and reservoirs /
The current project concentrates on the photodissociation of halocarbons CHBr₃, CF₂BrCF₂Br (sources of atmospheric halogens), halogen oxides ClO, BrO (active halogen species in the atmosphere) and finally chlorine nitrate ClONO₂ and bromine nitrate BrONO₂ (the two major temporary reservoirs for acti...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2003.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=765867551&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The current project concentrates on the photodissociation of halocarbons CHBr₃, CF₂BrCF₂Br (sources of atmospheric halogens), halogen oxides ClO, BrO (active halogen species in the atmosphere) and finally chlorine nitrate ClONO₂ and bromine nitrate BrONO₂ (the two major temporary reservoirs for active chlorine and bromine in the atmosphere), which play important roles in stratospheric and upper troposphere ozone chemistry. The experiments were performed primarily using a molecular beam time-of-flight mass spectroscopy machine with resonance enhanced multi-photon ionization detection methods which allows state specific detection of photofragments. Several experiments were carried out using a photofragment translational spectroscopy machine with VUV ionization detection at Advanced Light Source of Lawrence Berkeley National Laboratory. The VUV ionization is relatively soft comparing with electron impact but can still ionize most of the photofragments. In both experiments, products angular and speed distribution and their branching ratios were derived from the time-of-flight mass spectra. The results provide a direct measure of the photochemistry on the atmospheric halogen budget and assessment of their ozone depletion potential, which are critical for atmospheric composition modeling and forecasting. In addition, the experiments are capable of providing deep insight into fundamental questions of unimolecular dissociation, i.e. the nature of the excited states, the potential energy surfaces and their role in energy partitioning, and secondary decomposition. High level theoretical calculations were performed for the bond energies of chlorine and bromine nitrates and some of the unstable species involved in the dissociations cis-ClONO, trans-ClONO, cis-BrONO, and trans-BrONO, which are extremely difficult to obtain from experimental studies. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xvi, 186 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 170-185). |