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Yields of HONO₂ and HOONO Products from the Reaction of HO₂ and NO Using Pulsed Laser Photolysis and Mid-Infrared Cavity-Ringdown Spectroscopy

Mertens, Laura A. and Winiberg, Frank A. F. and Allen, Hannah M. and Sander, Stanley P. and Okumura, Mitchio (2022) Yields of HONO₂ and HOONO Products from the Reaction of HO₂ and NO Using Pulsed Laser Photolysis and Mid-Infrared Cavity-Ringdown Spectroscopy. Journal of Physical Chemistry A, 126 (40). pp. 7342-7360. ISSN 1089-5639. doi:10.1021/acs.jpca.2c04643.

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The reaction of HO₂ with NO is one of the most important steps in radical cycling throughout the stratosphere and troposphere. Previous literature experimental work revealed a small yield of nitric acid (HONO₂) directly from HO₂ + NO. Atmospheric models previously treated HO₂ + NO as radical recycling, but inclusion of this terminating step had large effects on atmospheric oxidative capacity and the concentrations of HONO₂ and ozone (O₃), among others. Here, the yield of HONO₂, φHONO₂, from the reaction of HO₂ + NO was investigated in a flow tube reactor using mid-IR pulsed-cavity ringdown spectroscopy. HO₂, produced by pulsed laser photolysis of Cl₂ in the presence of methanol, reacted with NO in a buffer gas mixture of N₂ and CO between 300 and 700 Torr at 278 and 300 K. HONO₂ and its weakly bound isomer HOONO were directly detected by their v1 absorption bands in the mid-IR region. CO was used to suppress HONO₂ produced from OH + NO₂ and exploit a chemical amplification scheme, converting OH back to HO₂. Under the experimental conditions described here, no evidence for the formation of either HONO₂ or HOONO was observed from HO₂ + NO. Using a comprehensive chemical model, constrained by observed secondary reaction products, all HONO₂ detected in the system could be accounted for by OH + NO₂. At 700 ± 14 Torr and 300 ± 3 K, φHONO₂ = 0.00 ± 0.11% (2σ) with an upper limit of 0.11%. If all of the observed HONO₂ was attributed to the HO₂ + NO reaction, φHONO₂ = 0.13 ± 0.07% with an upper limit of 0.20%. At 278 ± 2 K and 718 ± 14 Torr, we determine an upper limit, φHONO₂ ≤ 0.37%. Our measurements are significantly lower than those previously reported, lying outside of the uncertainty of the current experimental and recommended literature values.

Item Type:Article
Related URLs:
URLURL TypeDescription
Mertens, Laura A.0000-0003-4166-3954
Winiberg, Frank A. F.0000-0003-2801-5581
Allen, Hannah M.0000-0002-4218-5133
Sander, Stanley P.0000-0003-1424-3620
Okumura, Mitchio0000-0001-6874-1137
Additional Information:Financial support was provided by the National Aeronautics and Space Administration (NASA) Upper Atmosphere Research Program Grants (NNG06GD88G and NNX09AE21G), the NSF Graduate Research Fellowship Program (L.A.M.), and the USRA run NASA Postdoctoral Program (F.A.F.W.). Part of this research was performed at the NASA Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. We thank Ralph Page for improvements of the laser setup, Luis Gomez for design of the temperature-controlled cell, Michael Roy for machining assistance, and Richard Gerhard for glassware construction and repair. We also thank Professors Georges LeBras and John Barker for enlightening conversations.
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
NASA Postdoctoral ProgramUNSPECIFIED
Issue or Number:40
Record Number:CaltechAUTHORS:20221103-652750400.31
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ID Code:117707
Deposited By: Research Services Depository
Deposited On:17 Nov 2022 17:40
Last Modified:17 Nov 2022 17:40

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