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dc.contributor.advisorBetterton, Eric A.en_US
dc.contributor.authorGast, Karl Frederick, 1961-
dc.creatorGast, Karl Frederick, 1961-en_US
dc.date.accessioned2013-04-18T09:44:49Z
dc.date.available2013-04-18T09:44:49Z
dc.date.issued1997en_US
dc.identifier.urihttp://hdl.handle.net/10150/282404
dc.description.abstractThe development and investigation of a new technique for measuring tropospheric concentrations of hydroxyl radicals (OH) is presented. The technique is based on the near-infrared fluorescence of IR125 which is quenched upon reaction with OH. IR125, is shown to react with OH, and be sufficiently less reactive with other tropospheric oxidants that when exposed to tropospheric air samples, changes in the dye fluorescence are related to the ambient OH concentration. A near-infrared fluorimeter was constructed to determine IR125 concentrations. Detection of 10-12 M IR125 in solution was obtained. This sensitivity allows observation of changes in IR125 concentrations due to reaction with typical tropospheric OH concentrations. Changes in the fluorescence of IR125 when sampling the ambient air using dye impregnated quartz wool cartridges were shown to follow predicted OH concentrations for the observed environmental conditions. Photodecomposition by sunlight and reaction with other, longer lived, oxidants were accounted for in determining the IR125 response to OH. An OH source of known concentration to calibrate the IR125 response based on the photolysis of HONO or H2 was constructed. A photochemical computer model developed and used to determine the steady-state OH concentrations was validated by the successful prediction of concentrations of some cogenerated compounds. This OH source was not compatible with the sampling technique using dye impregnated quartz wool cartridges, because of the overwhelming interference caused by suspected heterogeneous reactions of the precursors. Absolute calibration remains to be completed.
dc.language.isoen_USen_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.subjectPhysics, Atmospheric Science.en_US
dc.titleOH detection by near-infrared fluorescence quenching of a polymethine dyeen_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
thesis.degree.grantorUniversity of Arizonaen_US
thesis.degree.leveldoctoralen_US
dc.identifier.proquest9806778en_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineAtmospheric Sciencesen_US
thesis.degree.namePh.D.en_US
dc.identifier.bibrecord.b37528890en_US
refterms.dateFOA2018-06-12T17:58:32Z
html.description.abstractThe development and investigation of a new technique for measuring tropospheric concentrations of hydroxyl radicals (OH) is presented. The technique is based on the near-infrared fluorescence of IR125 which is quenched upon reaction with OH. IR125, is shown to react with OH, and be sufficiently less reactive with other tropospheric oxidants that when exposed to tropospheric air samples, changes in the dye fluorescence are related to the ambient OH concentration. A near-infrared fluorimeter was constructed to determine IR125 concentrations. Detection of 10-12 M IR125 in solution was obtained. This sensitivity allows observation of changes in IR125 concentrations due to reaction with typical tropospheric OH concentrations. Changes in the fluorescence of IR125 when sampling the ambient air using dye impregnated quartz wool cartridges were shown to follow predicted OH concentrations for the observed environmental conditions. Photodecomposition by sunlight and reaction with other, longer lived, oxidants were accounted for in determining the IR125 response to OH. An OH source of known concentration to calibrate the IR125 response based on the photolysis of HONO or H2 was constructed. A photochemical computer model developed and used to determine the steady-state OH concentrations was validated by the successful prediction of concentrations of some cogenerated compounds. This OH source was not compatible with the sampling technique using dye impregnated quartz wool cartridges, because of the overwhelming interference caused by suspected heterogeneous reactions of the precursors. Absolute calibration remains to be completed.


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