Winiberg, F.A.F., Warman, W.J., Brumby, C.A. et al. (6 more authors) (2023) Comparison of temperature-dependent calibration methods of an instrument to measure OH and HO₂ radicals using laser-induced fluorescence spectroscopy. Atmospheric Measurement Techniques, 16 (19). pp. 4375-4390. ISSN 1867-1381
Abstract
Laser-induced fluorescence (LIF) spectroscopy has been widely applied to fieldwork measurements of OH radicals and HO2, following conversion to OH, over a wide variety of conditions, on different platforms and in simulation chambers. Conventional calibration of HOx (OH + HO2) instruments has mainly relied on a single method, generating known concentrations of HOx from H2O vapour photolysis in a flow of zero air impinging just outside the sample inlet (SHOx = CHOx . [HOx ], where SHOx is the observed signal and CHOx is the calibration factor). The fluorescence assay by gaseous expansion (FAGE) apparatus designed for HOx measurements in the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC) at the University of Leeds has been used to examine the sensitivity of FAGE to external gas temperatures (266–348 K). The conventional calibration methods give the temperature dependence of COH (relative to the value at 293 K) of (0.0059±0.0015) K−1 and CHO2 of (0.014±0.013) K−1. Errors are 2σ . COH was also determined by observing the decay of hydrocarbons (typically cyclohexane) caused by OH reactions giving COH (again, relative to the value at 293 K) of (0.0038 ± 0.0007) K−1. Additionally, CHO2 was determined based on the second-order kinetics of HO2 recombination with the temperature dependence of CHO2 , relative to 293 K being (0.0064 ± 0.0034) K−1. The temperature dependence of CHOx depends on the HOx number density, quenching, the relative population of the probed OH rotational level and HOx transmission from the inlet to the detection axis. The first three terms can be calculated and, in combination with the measured values of CHOx, show that HOx transmission increases with temperature. Comparisons with other instruments and the implications of this work are discussed.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © Author(s) 2023. This work is distributed under the Creative Commons Attribution 4.0 License. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemistry (Leeds) > Physical Chemistry (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 18 Oct 2023 08:55 |
Last Modified: | 18 Oct 2023 08:55 |
Status: | Published |
Publisher: | Copernicus |
Identification Number: | 10.5194/amt-16-4375-2023 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:204315 |
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