Ã−X̃Absorption of Propargyl Peroxy Radical (H−C≡C−CH2OO·): A Cavity Ring-Down Spectroscopic and Computational Study

2010 ◽  
Vol 114 (47) ◽  
pp. 12437-12446 ◽  
Author(s):  
Phillip S. Thomas ◽  
Neal D. Kline ◽  
Terry A. Miller
Keyword(s):  
Computational Study ◽  
Peroxy Radical ◽  
Cavity Ring Down

scholarly journals Computational study on the mechanism and kinetics for the reaction between HO2 and n-propyl peroxy radical

RSC Advances ◽  
2019 ◽  
Vol 9 (69) ◽  
pp. 40437-40444
Author(s):  
Zhenli Yang ◽  
Xiaoxiao Lin ◽  
Jiacheng Zhou ◽  
Mingfeng Hu ◽  
Yanbo Gai ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Temperature Regime ◽  
Computational Study ◽  
Peroxy Radical ◽  
Negative Temperature ◽  
Mechanism And Kinetics ◽  
Lower Temperature

The negative temperature dependence for the HO2 + n-C3H7O2 reaction in lower temperature regime.

Computational Study on the Existence of Organic Peroxy Radical-Water Complexes (RO2·H2O)

2008 ◽  
Vol 112 (7) ◽  
pp. 1587-1595 ◽  
Author(s):  
Jared Clark ◽  
Alecia M. English ◽  
Jaron C. Hansen ◽  
Joseph S. Francisco
Keyword(s):  
Computational Study ◽  
Peroxy Radical

scholarly journals Quantification of peroxynitric acid and peroxyacyl nitrates using an ethane-based thermal dissociation peroxy radical chemical amplification cavity ring-down spectrometer

2018 ◽  
Vol 11 (7) ◽  
pp. 4109-4127
Author(s):  
Youssef M. Taha ◽  
Matthew T. Saowapon ◽  
Faisal V. Assad ◽  
Connie Z. Ye ◽  
Xining Chen ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Thermal Dissociation ◽  
Peroxy Radical ◽  
Ambient Air ◽  
Oh Radicals ◽  
Ionization Mass ◽  
Chemical Amplification ◽  
Peroxynitric Acid ◽  
Peroxyacyl Nitrates ◽  
Cavity Ring Down

Abstract. Peroxy and peroxyacyl nitrates (PNs and PANs) are important trace gas constituents of the troposphere which are challenging to quantify by differential thermal dissociation with NO2 detection in polluted (i.e., high-NOx) environments. In this paper, a thermal dissociation peroxy radical chemical amplification cavity ring-down spectrometer (TD-PERCA-CRDS) for sensitive and selective quantification of total peroxynitrates (ΣPN  =  ΣRO2NO2) and of total peroxyacyl nitrates (ΣPAN  =  ΣRC(O)O2NO2) is described. The instrument features multiple detection channels to monitor the NO2 background and the ROx ( =  HO2 + RO2 + ΣRO2) radicals generated by TD of ΣPN and/or ΣPAN. Chemical amplification is achieved through the addition of 0.6 ppm NO and 1.6 % C2H6 to the inlet. The instrument's performance was evaluated using peroxynitric acid (PNA) and peroxyacetic or peroxypropionic nitric anhydride (PAN or PPN) as representative examples of ΣPN and ΣPAN, respectively, whose abundances were verified by iodide chemical ionization mass spectrometry (CIMS). The amplification factor or chain length increases with temperature up to 69 ± 5 and decreases with analyte concentration and relative humidity (RH). At inlet temperatures above 120 and 250 °C, respectively, PNA and ΣPAN fully dissociated, though their TD profiles partially overlap. Furthermore, interference from ozone (O3) was observed at temperatures above 150 °C, rationalized by its partial dissociation to O atoms which react with C2H6 to form C2H5 and OH radicals. Quantification of PNA and ΣPAN in laboratory-generated mixtures containing O3 was achieved by simultaneously monitoring the TD-PERCA responses in multiple parallel CRDS channels set to different temperatures in the 60 to 130 °C range. The (1 s, 2σ) limit of detection (LOD) of TD-PERCA-CRDS is 6.8 pptv for PNA and 2.6 pptv for ΣPAN and significantly lower than TD-CRDS without chemical amplification. The feasibility of TD-PERCA-CRDS for ambient air measurements is discussed.

scholarly journals Trace explosives detection by cavity ring-down spectroscopy (CRDS)

2021 ◽  
Author(s):  
Bobbi Stromer ◽  
Anthony Bednar ◽  
Milo Janjic ◽  
Scott Becker ◽  
Tamara Kylloe ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Limit Of Detection ◽  
Peroxy Radical ◽  
Peak Height ◽  
Expected Value ◽  
Explosives Detection ◽  
Triacetone Triperoxide ◽  
Radical Chain ◽  
Cavity Ring Down Spectroscopy ◽  
Cavity Ring Down

We built three successive versions of a thermal decomposition cavity ring-down spectrometer and tested their response to explosives. These explosive compound analyzers successfully detected nitroglycerine, 2,4,6-trinitrotoluene (TNT), pentaerythryl tetranitrate, hexahydro-1,3,5-trinitro-s-triazine and triacetone triperoxide (TATP). We determined the pathlength and limits of detection for each, with the best limit of detection being 13 parts per trillion (ppt) of TNT. For most of the explosive tests, the peak height was higher than the expected value, meaning that peroxy radical chain propagation was occurring with each of the explosives and not just the peroxide TATP.

a-pinene autoxidation at sub-second time-scales

2020 ◽  
Author(s):  
Matti Rissanen ◽  
Shawon Barua ◽  
Jordan Krechmer ◽  
Theo Kurtén ◽  
Siddharth Iyer
Keyword(s):  
Reaction Time ◽  
Organic Compounds ◽  
Time Scales ◽  
Chemical Ionization ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Computational Study ◽  
Peroxy Radical ◽  
Organic Aerosol ◽  
Ionization Mass

<p>Atmospheric aerosols impact climate and health. Most of the smallest atmospheric nanoparticles are formed by oxidation of volatile organic compounds (VOC) and subsequent condensation of resulting low-volatile vapors. Biogenic terpenes are the largest atmospheric secondary organic aerosol (SOA) source, and among these, a-pinene likely the single most important compound.</p><p> Recently, autoxidation changed the paradigm of long processing time-scales in the formation of SOA [1, 2]. Previous experiments with cyclic unsaturated compounds have indicated the autoxidation to be very rapid, forming compounds with even 10 O-atoms infused to the carbon structure in a few seconds timeframe [3-6]. Berndt et al. noted that the whole process was apparently finished already at about 1.5 seconds reaction time in cyclohexene ozonolysis initiated autoxidation, indicated by the “frozen” peroxy radical product distribution beyond this reaction time [4].</p><p>Here we performed sub-second time-scale flow reactor experiments of a-pinene ozonolysis initiated autoxidation under ambient atmospheric conditions to constrain the timeframe needed to form the first highly-oxidized reaction products, and to inspect the peroxy radical dynamics at significantly shorter reaction times than have been previously possible. The shortest achievable reaction time was around 0.1 seconds and was enabled by the new Multi-scheme chemical IONization (MION) inlet setup [7]. Nitrate and bromide were used as reagent ions in this work.</p><p> </p><p><strong>References:</strong></p><ol><li>J. D. Crounse, et al. Autoxidation of Organic Compounds in the Atmosphere, J. Phys. Chem. Lett., 2013, 4, 3513-3520.</li> <li>M. Ehn, et al. A large source of low-volatility secondary organic aerosol, Nature, 2014, 506, 476-479.</li> <li>M. P. Rissanen, et al. The formation of highly oxidized multifunctional products in the ozonolysis of cyclohexene, J. Am. Chem. Soc., 2014, 136, 15596-15606.</li> <li>T. Berndt, et al. Gas-Phase Ozonolysis of Cycloalkenes: Formation of Highly Oxidized RO<sub>2</sub> Radicals and Their Reactions with NO, NO<sub>2</sub>, SO<sub>2</sub>, and Other RO<sub>2</sub> Radicals, J. Phys. Chem. A, 2015, 119, 10336-10348.</li> <li>M. P. Rissanen, et al. Kulmala, Effects of Chemical Complexity on the Autoxidation Mechanisms of Endocyclic Alkene Ozonolysis Products: From Methylcyclohexenes toward Understanding α-Pinene, J. Phys. Chem. A, 2015, 119, 4633-4650.</li> <li>T. Kurtén, et al. Computational Study of Hydrogen Shifts and Ring-Opening Mechanisms in α-Pinene Ozonolysis Products, J. Phys. Chem. A, 2015, 119, 11366-11375.</li> <li>M. P. Rissanen, et al. Multi-scheme chemical ionization inlet (MION) for fast switching of reagent ion chemistry in atmospheric pressure chemical ionization mass spectrometry (CIMS) applications, Atmos. Meas. Tech., 2019, 12, 6635-6646.</li> </ol>

scholarly journals Airborne measurement of peroxy radicals using chemical amplification coupled with cavity ring-down spectroscopy: the PeRCEAS instrument

2020 ◽  
Vol 13 (5) ◽  
pp. 2577-2600 ◽  
Author(s):  
Midhun George ◽  
Maria Dolores Andrés Hernández ◽  
Vladyslav Nenakhov ◽  
Yangzhuoran Liu ◽  
John Philip Burrows
Keyword(s):  
Oxidation Mechanism ◽  
Peroxy Radical ◽  
Ambient Air ◽  
Peroxy Radicals ◽  
Free Troposphere ◽  
Cavity Ring Down Spectroscopy ◽  
Airborne Measurements ◽  
Dual Channel ◽  
Unpaired Spin ◽  
Cavity Ring Down

Abstract. Hydroperoxyl (HO2) and organic peroxy (RO2) radicals have an unpaired spin and are highly reactive free radicals. Measurements of the sum of HO2 and RO2 provide unique information about the chemical processing in an air mass. This paper describes the experimental features and capabilities of the Peroxy Radical Chemical Enhancement and Absorption Spectrometer (PeRCEAS). This is an instrument designed to make measurements on aircraft from the boundary layer to the lower stratosphere. PeRCEAS combines the amplified conversion of peroxy radicals to nitrogen dioxide (NO2) with the sensitive detection of NO2 using cavity ring-down spectroscopy (CRDS) at 408 nm. PeRCEAS is a dual-channel instrument, with two identical reactor–detector lines working out of phase with one another at a constant and defined pressure lower than ambient at the aircraft altitude. The suitability of PeRCEAS for airborne measurements in the free troposphere was evaluated by extensive characterisation and calibration under atmospherically representative conditions in the laboratory. The use of alternating modes of the two instrumental channels successfully captures short-term variations in the sum of peroxy radicals, defined as RO2∗ (RO2∗=HO2+∑RO2+OH+∑RO, with R being an organic chain) in ambient air. For a 60 s measurement, the RO2∗ detection limit is < 2 pptv for a minimum (2σ) NO2 detectable mixing ratio < 60 pptv, under laboratory conditions in the range of atmospheric pressures and temperatures expected in the free troposphere. PeRCEAS has been successfully deployed within the OMO (Oxidation Mechanism Observations) and EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional and Global scales) missions in different airborne campaigns aboard the High Altitude LOng range research aircraft (HALO) for the study of the composition of the free troposphere.

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