Broadband optical cavity absorption spectroscopy in the near-ultraviolet: applications in atmospheric chemistry

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dc.contributor.advisor Venables, Dean S. Chen, Jun 2011-10-03T16:05:31Z 2011-10-03T16:05:31Z 2011 2011-09-27
dc.identifier.citation Chen, J., 2011. Broadband optical cavity absorption spectroscopy in the near-ultraviolet: applications in atmospheric chemistry. PhD Thesis, University College Cork. en
dc.description.abstract A novel spectroscopic method, incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS), has been modified and extended to measure absorption spectra in the near-ultraviolet with high sensitivity. The near-ultraviolet region extends from 300 to 400 nm and is particularly important in tropospheric photochemistry; absorption of near-UV light can also be exploited for sensitive trace gas measurements of several key atmospheric constituents. In this work, several IBBCEAS instruments were developed to record reference spectra and to measure trace gas concentrations in the laboratory and field. An IBBCEAS instrument was coupled to a flow cell for measuring very weak absorption spectra between 335 and 375 nm. The instrument was validated against the literature absorption spectrum of SO2. Using the instrument, we report new absorption cross-sections of O3, acetone, 2-butanone, and 2-pentanone in this spectral region, where literature data diverge considerably owing to the extremely weak absorption. The instrument was also applied to quantifying low concentrations of the short-lived radical, BrO, in the presence of strong absorption by Br2 and O3. A different IBBCEAS system was adapted to a 4 m3 atmosphere simulation chamber to record the absorption cross-sections of several low vapour pressure compounds, which are otherwise difficult to measure. Absorption cross-sections of benzaldehyde and the more volatile alkyl nitrites agree well with previous spectra; on this basis, the cross-sections of several nitrophenols are reported for the first time. In addition, the instrument was also used to study the optical properties of secondary organic aerosol formed following the photooxidation of isoprene. An extractive IBBCEAS instrument was developed for detecting HONO and NO2 and had a sensitivity of about 10-9 cm-1. This instrument participated in a major international intercomparison of HONO and NO2 measurements held in the EUPHORE simulation chamber in Valencia, Spain, and results from that campaign are also reported here. en
dc.description.sponsorship Science Foundation Ireland (06/RFP/CHP055) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2011, Jun Chen en
dc.rights.uri en
dc.subject BBCEAS en
dc.subject Near-ultraviolet en
dc.subject Cross-section en
dc.subject Broadband cavity enhanced absorption spectroscopy en
dc.subject Spectroscopy en
dc.subject.lcsh Atmospheric chemistry en
dc.subject.lcsh Spectrum analysis en
dc.subject.lcsh Absorption spectra en
dc.title Broadband optical cavity absorption spectroscopy in the near-ultraviolet: applications in atmospheric chemistry en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD (Chemistry) en
dc.internal.availability Full text available en
dc.description.version Accepted Version en
dc.contributor.funder Science Foundation Ireland en
dc.contributor.funder European Commission en
dc.description.status Not peer reviewed en Chemistry en
dc.relation.project info:eu-repo/grantAgreement/EC/FP7::SP4::INFRA/228335/EU/Integration of European Simulation Chambers for Investigating Atmospheric Processes - Part 2/EUROCHAMP-2

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