Detection of iodine monoxide radicals in the marine boundary layer using laser induced fluorescence spectroscopy |
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| Authors: | Lisa K Whalley Kate L Furneaux Tom Gravestock Helen M Atkinson Catherine S E Bale Trevor Ingham William J Bloss Dwayne E Heard |
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| Institution: | (1) School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK;(2) School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK |
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| Abstract: | A Laser Induced Fluorescence (LIF) instrument has been developed to detect iodine monoxide (IO) radicals in the atmosphere.
An all solid-state Nd:YAG pumped Ti:Sapphire laser operating at approximately 445 nm was used to excite the (2,0) band of
the IO A2Π3/2 ← X2Π3/2 electronic transition, with off-resonance fluorescence in the (2,5) band detected at 521 nm. The sensitivity of the instrument
was determined by calibration. IO (between 10 and 150 pptV) was generated following the 184.9 nm photolysis of N2O/CF3I/N2 mixtures with O3 actinometry used to determine the photolysis flux. The detection limit was determined to be 0.3 pptV for a 300 s integration
period, with an uncertainty of 23% (1σ). The instrument was deployed in August/September 2006 during the RHaMBLe (Reactive Halogens in the Marine Boundary Layer)
campaign in Roscoff, France. Located on a small jetty, a few metres from the water’s edge at high tide, the instrument measured
significant levels of IO on 11 days, with a maximum of 27.6 ± 3.2 pptV observed on one day (averaged over 10 s) representing
the highest IO mixing ratio recorded in the marine boundary layer to date. IO displayed a clear diurnal profile with a maximum
at low tide during the daytime. These results represent the first point measurements of IO in the atmosphere by LIF. |
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| Keywords: | Free-radicals Iodine monoxide Laser induced fluorescence Marine boundary layer RHaMBLe |
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