Observation of the electronic transition of C6–C10 peroxy radicals

Kline, Neal D.; Miller, Terry A.

doi:10.1016/j.cplett.2014.03.087

“…Whilst a great deal of work has been performed identifying the absorbance features of RO 2 in the near IR (e.g. Kline and Miller, 2014), to date there has been almost no laboratory evidence of HO x formation following absorption by RO 2 in the near IR. However, Maccarone et al (2013) recently showed that arylperoxy radicals (RO 2 derived from aromatic hydrocarbons) are able to photodissociate in the visible spectrum to yield O( 3 P) and hence produce O 3 in the troposphere, without the need for NO x .…”

Section: Radical Chemistry Radical Changesmentioning

confidence: 99%

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

Monks¹,

Archibald²,

Colette³

et al. 2014

Preprint

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Abstract. Ozone holds a certain fascination in atmospheric science. It is ubiquitous in the atmosphere, central to tropospheric oxidation chemistry, yet harmful to human and ecosystem health as well as being an important greenhouse gas. It is not emitted into the atmosphere but is a by-product of the very oxidation chemistry it largely initiates. Much effort is focussed on the reduction of surface levels of ozone owing to its health impacts but recent efforts to achieve reductions in exposure at a country scale have proved difficult to achieve due to increases in background ozone at the zonal hemispheric scale. There is also a growing realisation that the role of ozone as a short-lived climate pollutant could be important in integrated air quality climate-change mitigation. This review examines current understanding of the processes regulating tropospheric ozone at global to local scales from both measurements and models. It takes the view that knowledge across the scales is important for dealing with air quality and climate change in a synergistic manner.

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“…The CRDS technique has been used under both ambient and jet-cooled conditions to provide insight into the molecular structure of CH 3 O 2 and more complex RO 2 , as well as to selectively measure [RO 2 ] in the laboratory (Sharp et al, 2008;Kline and Miller, 2014;Pushkarsky et al, 2000;Farago et al, 2013;Atkinson and Spillman, 2002;Sprague et al, 2013). Good agreement has been found between the experimental spectrum of CH 3 O 2 in the range between ∼ 7200-8600 cm −1 (∼ 1.18-1.40 µm) measured using pulsed CRDS at typically 200 mbar of N 2 /O 2 = 1.5 : 1.0 and theoretical predictions (Chung et al, 2007;Sharp et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

An intercomparison of CH₃O₂ measurements by fluorescence assay by gas expansion and cavity ring-down spectroscopy within HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)

Onel

¹

,

Brennan

²

,

Gianella

³

et al. 2020

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Abstract. Simultaneous measurements of CH3O2 radical concentrations have been performed using two different methods in the Leeds HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry) chamber at 295 K and in 80 mbar of a mixture of 3:1 He∕O2 and 100 or 1000 mbar of synthetic air. The first detection method consisted of the indirect detection of CH3O2 using the conversion of CH3O2 into CH3O by excess NO with subsequent detection of CH3O by fluorescence assay by gas expansion (FAGE). The FAGE instrument was calibrated for CH3O2 in two ways. In the first method, a known concentration of CH3O2 was generated using the 185 nm photolysis of water vapour in synthetic air at atmospheric pressure followed by the conversion of the generated OH radicals to CH3O2 by reaction with CH4∕O2. This calibration can be used for experiments performed in HIRAC at 1000 mbar in air. In the second method, calibration was achieved by generating a near steady state of CH3O2 and then switching off the photolysis lamps within HIRAC and monitoring the subsequent decay of CH3O2, which was controlled via its self-reaction, and analysing the decay using second-order kinetics. This calibration could be used for experiments performed at all pressures. In the second detection method, CH3O2 was measured directly using cavity ring-down spectroscopy (CRDS) using the absorption at 7487.98 cm−1 in the A←X (ν12) band with the optical path along the ∼1.4 m chamber diameter. Analysis of the second-order kinetic decays of CH3O2 by self-reaction monitored by CRDS has been used for the determination of the CH3O2 absorption cross section at 7487.98 cm−1, both at 100 mbar of air and at 80 mbar of a 3:1 He∕O2 mixture, from which σCH3O2=(1.49±0.19)×10-20 cm2 molecule−1 was determined for both pressures. The absorption spectrum of CH3O2 between 7486 and 7491 cm−1 did not change shape when the total pressure was increased to 1000 mbar, from which we determined that σCH3O2 is independent of pressure over the pressure range 100–1000 mbar in air. CH3O2 was generated in HIRAC using either the photolysis of Cl2 with UV black lamps in the presence of CH4 and O2 or the photolysis of acetone at 254 nm in the presence of O2. At 1000 mbar of synthetic air the correlation plot of [CH3O2]FAGE against [CH3O2]CRDS gave a gradient of 1.09±0.06. At 100 mbar of synthetic air the FAGE–CRDS correlation plot had a gradient of 0.95±0.024, and at 80 mbar of 3:1 He∕O2 mixture the correlation plot gradient was 1.03±0.05. These results provide a validation of the FAGE method to determine concentrations of CH3O2.

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“…Whilst a great deal of work has been performed identifying the absorbance features of RO 2 in the near IR (e.g. Kline and Miller, 2014), to date there has been almost no laboratory evidence of HO x formation following absorption by RO 2 in the near IR. However, Maccarone et al (2013) recently showed that arylperoxy radicals (RO 2 derived from aromatic hydrocarbons) are able to photodissociate in the visible spectrum to yield O( 3 P) and hence produce O 3 in the troposphere, without the need for NO x .…”

Section: Radical Chemistry Radical Changesmentioning

confidence: 99%

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

Monks

¹

,

Archibald

²

,

Colette

³

et al. 2015

View full text Add to dashboard Cite

Abstract. Ozone holds a certain fascination in atmospheric science. It is ubiquitous in the atmosphere, central to tropospheric oxidation chemistry, yet harmful to human and ecosystem health as well as being an important greenhouse gas. It is not emitted into the atmosphere but is a byproduct of the very oxidation chemistry it largely initiates. Much effort is focused on the reduction of surface levels of ozone owing to its health and vegetation impacts, but recent efforts to achieve reductions in exposure at a country scale have proved difficult to achieve owing to increases in background ozone at the zonal hemispheric scale. There is also a growing realisation that the role of ozone as a short-lived climate pollutant could be important in integrated air quality climate change mitigation. This review examines current understanding of the processes regulating tropospheric ozone at global to local scales from both measurements and models. It takes the view that knowledge across the scales is important for dealing with air quality and climate change in a synergistic manner. The review shows that there remain a number of clear challenges for ozone such as explaining surface trends, incorporating new chemical understanding, ozone-climate coupling, and a better assessment of impacts. There is a clear and present need to treat ozone across the range of scales, a transboundary issue, but with an emphasis on the hemispheric scales. New observational opportunities are offered both by satellites and small sensors that bridge the scales.

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Observation of the electronic transition of C6–C10 peroxy radicals

Cited by 6 publications

References 25 publications

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

An intercomparison of CH₃O₂ measurements by fluorescence assay by gas expansion and cavity ring-down spectroscopy within HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

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Observation of the electronic transition of C6–C10 peroxy radicals

Cited by 6 publications

References 25 publications

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

An intercomparison of CH3O2 measurements by fluorescence assay by gas expansion and cavity ring-down spectroscopy within HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)

Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer

Contact Info

Product

Resources

About

An intercomparison of CH₃O₂ measurements by fluorescence assay by gas expansion and cavity ring-down spectroscopy within HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)