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Stuhr M, Friedrichs G. Mid-infrared Frequency Modulation Detection of HCN and Its Reaction with O Atoms behind Shock Waves. J Phys Chem A 2022; 126:9485-9496. [DOI: 10.1021/acs.jpca.2c06817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Michael Stuhr
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Straße 1, 24118Kiel, Germany
| | - Gernot Friedrichs
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Straße 1, 24118Kiel, Germany
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Chen TY, Lee YP. Dynamics of the reaction CH 2I + O 2 probed via infrared emission of CO, CO 2, OH and H 2CO. Phys Chem Chem Phys 2020; 22:17540-17553. [PMID: 32808958 DOI: 10.1039/d0cp01940b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction CH2I + O2 has been widely employed recently for the production of the simplest Criegee intermediate CH2OO in laboratories, but the detailed dynamics of this reaction have been little explored. Infrared emission of several products of this reaction, initiated on irradiation of CH2I2 and O2 (∼8 Torr) in a flowing mixture at 308 or 248 nm, was recorded with a step-scan Fourier-transform spectrometer; possible routes of formation were identified according to the observed vibrational distribution of products and published theoretical potential-energy schemes. Upon irradiation at 308 nm, Boltzmann distributions of CO (v ≤ 5, J ≤ 19) with an average vibrational energy of 32 ± 3 kJ mol-1 and OH (v ≤ 3, J ≤ 5.5) with an average vibrational energy of 29 ± 4 kJ mol-1 were observed and assigned to the decomposition of HCOOH* to form CO + H2O and OH + HCO, respectively. The broadband emission of CO2 was simulated with two vibrational distributions of average energies (91 ± 4) and (147 ± 8) kJ mol-1 and assigned to be produced from the decomposition of HCOOH* and methylene bis(oxy), respectively. Upon irradiation of samples at 248 nm, the emission of OH and CO2 showed similar distributions with slightly greater energies, but the distribution of CO (v ≤ 11, J ≤ 19) became bimodal with average vibrational energies of (23 ± 4) and (107 ± 29) kJ mol-1, and branching (56 ± 5) : (44 ± 5). The additional large-v component is assigned to be produced from a secondary reaction HCO + O2 to form CO + HO2; HCO is a coproduct of OH. The branching between CO and OH is (50 ± 5) : (50 ± 5) at 308 nm and (64 ± 5) : (36 ± 4) at 248 nm, consistent with the mechanism according to which an additional channel to produce CO opens at 248 nm. Highly internally excited H2CO was also observed. With O2 at 16 Torr, the extrapolated nascent internal distributions are similar to those with O2 at 8 Torr except for a slight quenching effect.
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Affiliation(s)
- Ting-Yu Chen
- Department of Applied Chemistry and Institute of Molecular Science National Chiao Tung University, Hsinchu 30010, Taiwan.
| | - Yuan-Pern Lee
- Department of Applied Chemistry and Institute of Molecular Science National Chiao Tung University, Hsinchu 30010, Taiwan. and Center for Emergent Functional Matter Science, National Chiao Tung University, Hsinchu 30010, Taiwan and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
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Faßheber N, Bornhorst L, Hesse S, Sakai Y, Friedrichs G. The Reaction NCN + H 2: Quantum Chemical Calculations, Role of 1NCN Chemistry, and 3NCN Absorption Cross Section. J Phys Chem A 2020; 124:4632-4645. [PMID: 32396349 DOI: 10.1021/acs.jpca.0c02631] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The NCN radical plays a key role for modeling prompt-NO formation in hydrocarbon flames. Recently, in a combined shock tube and flame modeling study, the so far neglected reaction NCN + H2 and the related chemistry of the main product HNCN turned out to be significant for NO modeling under fuel-rich conditions. In this study, the reaction has been thoroughly revisited by detailed quantum chemical rate constant calculations both for the singlet 1NCN and triplet 3NCN pathways. Optimized geometries and vibrational frequencies of reactants, products, and transition states were calculated on B3LYP/aug-cc-pVQZ level with single-point energy calculations carried out against the optimized structures using CASPT2/aug-cc-pVQZ. The determined rate constants for the 1NCN + H2 reaction as well as the newly measured high temperature absorption cross section of 3NCN made a reevaluation of the shock tube data of the previous work necessary, finally revealing quantitative agreement between experiment and theory. Moreover, the new directly measured Doppler-limited absorption cross section data, σ(3NCN, λ = 329.1302 nm) = 2.63 × 109 × exp(-1.96 × 10-3 × T/K) cm2/mol (±23%, p = 0 bar, T = 870-1700 K), are in agreement with previously reported values based on detailed spectroscopic simulations. Hence, a long-standing debate about a reliable high temperature 3NCN absorption cross section has been resolved. Whereas 3NCN + H2 resembles a simple abstraction type reaction with the exclusive products HNCN + H, the singlet radical reaction is initiated by the insertion into the H-H bond. Up to pressures of 100 bar, the main products of the subsequent decomposition of the H2NCN intermediate are HNCN + H as well, with minor contributions of CN + NH2 toward higher temperatures. Although much faster than the triplet reaction, the singlet radical insertion is actually rather slow, due to the necessary reorganization of the HOMO electron density in 1NCN that is equally distributed over the two N atom sites. In general, the distinct reactivity differences call for a separate treatment of 1NCN and 3NCN chemistry. However, as the main reaction products in case of the H2 reaction are the same and as the population of the 1NCN in thermal equilibrium remains low, a properly weighted effective rate constant k(NCN + H2 → HNCN + H) = 2.62 × 104 × (T/K)2.78 × exp(-97.6 kJ/mol/RT) cm3 mol-1s-1(±30%, 800 K < T < 3000 K, p < 100 bar) is recommended for inclusion into flame models that, as yet, do not explicitly account for 1NCN chemistry.
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Affiliation(s)
- Nancy Faßheber
- Institute of Physical Chemistry, Christian-Albrechts-University Kiel, Max-Eyth-Straße 1, 24118 Kiel, Germany
| | - Lars Bornhorst
- Institute of Physical Chemistry, Christian-Albrechts-University Kiel, Max-Eyth-Straße 1, 24118 Kiel, Germany
| | - Sebastian Hesse
- Institute of Physical Chemistry, Christian-Albrechts-University Kiel, Max-Eyth-Straße 1, 24118 Kiel, Germany
| | - Yasuyuki Sakai
- Department of Mechanical Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Gernot Friedrichs
- Institute of Physical Chemistry, Christian-Albrechts-University Kiel, Max-Eyth-Straße 1, 24118 Kiel, Germany
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Stuhr M, Faßheber N, Friedrichs G. Single-tone mid-infrared frequency modulation spectroscopy for sensitive detection of transient species. OPTICS EXPRESS 2019; 27:26499-26512. [PMID: 31674530 DOI: 10.1364/oe.27.026499] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 08/12/2019] [Indexed: 06/10/2023]
Abstract
A single-tone mid-infrared frequency modulation (MIR-FM) spectrometer consisting of a cw-OPO-based laser system, a 500 MHz LiTaO 3 electro-optical modulator (EOM), and a high-bandwidth GaAs mid-infrared detector has been developed. In order to assess the instrument's sensitivity and time resolution, FM spectra of selected CH 4 transitions around 3070 cm -1 were measured and the reaction Cl + CH 4 following the 193 nm excimer laser photolysis of oxalyl chloride was investigated by recording concentration-time profiles of HCl at 2925.90 cm -1 in a low-pressure slow-flow reactor. Furthermore, OH radicals were generated by UV photolysis of H 2O 2 and its transients were recorded at 3447.27 cm -1. The minimal detectable absorption of the spectrometer was determined to be A min=4⋅10-4 (Δ f BW=1 MHz, ν~=3447 cm -1) by using the Allan approach. Mainly due to thermal noise contributions of the easy-to-saturate photodetector, the detection limit is about a factor of 4 above the shot-noise limit. To the best of our knowledge, this work reports the first implementation of a single-tone MIR-FM spectrometer based on an external EOM modulation scheme and its use for the detection of transient molecular species.
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Ryu SO, Shin KS, Hwang SM. Determination of the Rate Coefficients of the CH4 + O2 → HO2 + CH3and HCO + O2 → HO2 + CO Reactions at High Temperatures. B KOREAN CHEM SOC 2017. [DOI: 10.1002/bkcs.11070] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Si-Ok Ryu
- School of Chemical Engineering; Yeungnam University; Gyeongbuk 712-749 Korea
| | - Kuan Soo Shin
- Department of Chemistry; Soongsil University; Seoul 156-743 Korea
- Department of Information Communication, Materials, and Chemistry Convergence Technology; Soongsil University; Seoul 156-743 Korea
| | - Soon Muk Hwang
- Science Applications International Corporation; 3000 Aerospace Parkway; Brook Park Ohio 44142 USA
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Faßheber N, Friedrichs G. Shock Tube Measurements of the Rate Constant of the Reaction NCN + O2. INT J CHEM KINET 2015. [DOI: 10.1002/kin.20932] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Nancy Faßheber
- Institut für Physikalische Chemie; Christian-Albrechts-Universität zu Kiel; 24118 Kiel Germany
| | - Gernot Friedrichs
- Institut für Physikalische Chemie; Christian-Albrechts-Universität zu Kiel; 24118 Kiel Germany
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Faßheber N, Friedrichs G, Marshall P, Glarborg P. Glyoxal Oxidation Mechanism: Implications for the Reactions HCO + O2 and OCHCHO + HO2. J Phys Chem A 2015; 119:7305-15. [DOI: 10.1021/jp512432q] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Nancy Faßheber
- Institute
of Physical Chemistry, Christian-Albrechts-Universität Kiel, Max-Eyth-Str. 1, 24118 Kiel, Germany
| | - Gernot Friedrichs
- Institute
of Physical Chemistry, Christian-Albrechts-Universität Kiel, Max-Eyth-Str. 1, 24118 Kiel, Germany
| | - Paul Marshall
- Department
of Chemistry and Center for Advanced Scientific Computing and Modeling
(CASCaM), University of North Texas, 1155 Union Circle #305070, Denton, Texas 76203−5017, United States
| | - Peter Glarborg
- Department
of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
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Faßheber N, Lamoureux N, Friedrichs G. The rate constant of the reaction NCN + H2 and its role in NCN and NO modeling in low pressure CH4/O2/N2-flames. Phys Chem Chem Phys 2015; 17:15876-86. [DOI: 10.1039/c5cp01414j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The high temperature rate constant of the so-far neglected reaction NCN + H2 has been measured for the first time and its influence on NOx flame modeling has been evaluated by implementation into the GDFkin3.0_NCN mechanism.
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Affiliation(s)
- Nancy Faßheber
- Institut für Physikalische Chemie
- Christian-Albrechts-Universität zu Kiel
- 24118 Kiel
- Germany
| | - Nathalie Lamoureux
- Laboratoire PC2A
- UMR8522 CNRS/Université Lille 1
- 59655 Villeneuve d'Ascq
- France
| | - Gernot Friedrichs
- Institut für Physikalische Chemie
- Christian-Albrechts-Universität zu Kiel
- 24118 Kiel
- Germany
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Faßheber N, Dammeier J, Friedrichs G. Direct measurements of the total rate constant of the reaction NCN + H and implications for the product branching ratio and the enthalpy of formation of NCN. Phys Chem Chem Phys 2014; 16:11647-57. [DOI: 10.1039/c4cp01107d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The high-temperature rate constant of the reaction NCN + H, a key reaction for modelling NOx formation in flames, has been directly measured for the first time.
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Affiliation(s)
- Nancy Faßheber
- Institut für Physikalische Chemie
- Christian-Albrechts-Universität zu Kiel
- 24118 Kiel, Germany
| | - Johannes Dammeier
- Institut für Physikalische Chemie
- Christian-Albrechts-Universität zu Kiel
- 24118 Kiel, Germany
| | - Gernot Friedrichs
- Institut für Physikalische Chemie
- Christian-Albrechts-Universität zu Kiel
- 24118 Kiel, Germany
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Affiliation(s)
- Akira Matsugi
- Department of Chemical System Engineering; School of Engineering, The University of Tokyo; 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan
- Research Institute of Science for Safety and Sustainability; National Institute of Advanced Industrial Science and Technology; 16-1 Onogawa Tsukuba Ibaraki 305-8569 Japan
| | - Akira Miyoshi
- Department of Chemical System Engineering; School of Engineering, The University of Tokyo; 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan
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Brumfield B, Sun W, Ju Y, Wysocki G. Direct In Situ Quantification of HO2 from a Flow Reactor. J Phys Chem Lett 2013; 4:872-876. [PMID: 26291349 DOI: 10.1021/jz400143c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The first direct in situ measurements of hydroperoxyl radical (HO2) at atmospheric pressure from the exit of a laminar flow reactor have been carried out using mid-infrared Faraday rotation spectroscopy. HO2 was generated by oxidation of dimethyl ether, a potential renewable biofuel with a simple molecular structure but rich low-temperature oxidation chemistry. On the basis of the results of nonlinear fitting of the experimental data to a theoretical spectroscopic model, the technique offers an estimated sensitivity of <1 ppmv over a reactor exit temperature range of 398-673 K. Accurate in situ measurement of this species will aid in quantitative modeling of low-temperature and high-pressure combustion kinetics.
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Affiliation(s)
- Brian Brumfield
- †Department of Electrical Engineering and ‡Department of Mechanical and Aerospace Engineering, Princeton University, Engineering Quadrangle, Princeton, New Jersey 08544, United States
| | - Wenting Sun
- †Department of Electrical Engineering and ‡Department of Mechanical and Aerospace Engineering, Princeton University, Engineering Quadrangle, Princeton, New Jersey 08544, United States
| | - Yiguang Ju
- †Department of Electrical Engineering and ‡Department of Mechanical and Aerospace Engineering, Princeton University, Engineering Quadrangle, Princeton, New Jersey 08544, United States
| | - Gerard Wysocki
- †Department of Electrical Engineering and ‡Department of Mechanical and Aerospace Engineering, Princeton University, Engineering Quadrangle, Princeton, New Jersey 08544, United States
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Salter RJ, Blitz MA, Heard DE, Kovács T, Pilling MJ, Rickard AR, Seakins PW. Quantum yields for the photolysis of glyoxal below 350 nm and parameterisations for its photolysis rate in the troposphere. Phys Chem Chem Phys 2013; 15:4984-94. [DOI: 10.1039/c3cp43597k] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Dammeier J, Oden B, Friedrichs G. A consistent model for the thermal decomposition of NCN3and the singlet- triplet relaxation of NCN. INT J CHEM KINET 2012. [DOI: 10.1002/kin.20739] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Dammeier J, Faßheber N, Friedrichs G. Direct measurements of the high temperature rate constants of the reactions NCN + O, NCN + NCN, and NCN + M. Phys Chem Chem Phys 2012; 14:1030-7. [DOI: 10.1039/c1cp22123j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Dammeier J, Friedrichs G. Direct Measurements of the Rate Constants of the Reactions NCN + NO and NCN + NO2 Behind Shock Waves. J Phys Chem A 2011; 115:14382-90. [DOI: 10.1021/jp208715c] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- J. Dammeier
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany
| | - G. Friedrichs
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany
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Baeza-Romero MT, Blitz MA, Goddard A, Seakins PW. Time-of-flight mass spectrometry for time-resolved measurements: Some developments and applications. INT J CHEM KINET 2011. [DOI: 10.1002/kin.20620] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Theoretical studies on the gas phase reaction mechanisms and kinetics of glyoxal with HO2 with water and without water. COMPUT THEOR CHEM 2011. [DOI: 10.1016/j.comptc.2011.01.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Tereza AM, Slutskii VG, Severin ES. Autoignition of ethylene in shock waves. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B 2010. [DOI: 10.1134/s1990793110030176] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Dammeier J, Friedrichs G. Thermal Decomposition of NCN3 as a High-Temperature NCN Radical Source: Singlet−Triplet Relaxation and Absorption Cross Section of NCN(3Σ). J Phys Chem A 2010; 114:12963-71. [DOI: 10.1021/jp1043046] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- J. Dammeier
- Institut für Physikalische Chemie, Olshausenstrasse 40, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
| | - G. Friedrichs
- Institut für Physikalische Chemie, Olshausenstrasse 40, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
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Salter RJ, Blitz MA, Heard DE, Pilling MJ, Seakins PW. New Chemical Source of the HCO Radical Following Photoexcitation of Glyoxal, (HCO)2. J Phys Chem A 2009; 113:8278-85. [DOI: 10.1021/jp9030249] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Robert J. Salter
- School of Chemistry, University of Leeds, Leeds, LS2 9 JT, United Kingdom
| | - Mark A. Blitz
- School of Chemistry, University of Leeds, Leeds, LS2 9 JT, United Kingdom
| | - Dwayne E. Heard
- School of Chemistry, University of Leeds, Leeds, LS2 9 JT, United Kingdom
| | - Michael J. Pilling
- School of Chemistry, University of Leeds, Leeds, LS2 9 JT, United Kingdom
| | - Paul W. Seakins
- School of Chemistry, University of Leeds, Leeds, LS2 9 JT, United Kingdom
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Rasmussen CL, Jakobsen JG, Glarborg P. Experimental measurements and kinetic modeling of CH4/O2and CH4/C2H6/O2conversion at high pressure. INT J CHEM KINET 2008. [DOI: 10.1002/kin.20352] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Friedrichs G, Colberg M, Dammeier J, Bentz T, Olzmann M. HCO formation in the thermal unimolecular decomposition of glyoxal: rotational and weak collision effects. Phys Chem Chem Phys 2008; 10:6520-33. [DOI: 10.1039/b809992h] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Li J, Zhao Z, Kazakov A, Chaos M, Dryer FL, Scire JJ. A comprehensive kinetic mechanism for CO, CH2O, and CH3OH combustion. INT J CHEM KINET 2007. [DOI: 10.1002/kin.20218] [Citation(s) in RCA: 588] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Dammeier J, Colberg M, Friedrichs G. Wide temperature range (T = 295 K and 770–1305 K) study of the kinetics of the reactions HCO + NO and HCO + NO2 using frequency modulation spectroscopy. Phys Chem Chem Phys 2007; 9:4177-88. [PMID: 17687467 DOI: 10.1039/b704197g] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The rate constants for , HCO + NO --> HNO + CO, and , HCO + NO(2)--> products, have been measured at temperatures between 770 K < T < 1305 K behind reflected shock waves and, for the purpose of a consistency check, in a slow flow reactor at room temperature. HCO radicals were generated by 193 nm excimer laser photolysis of diluted gas mixtures containing glyoxal, (CHO)(2), and NO or NO(2) in argon and were monitored using frequency modulation (FM) absorption spectroscopy. Kinetic simulations based on a comprehensive reaction mechanism showed that the rate constants for the title reactions could be sensitively extracted from the measured HCO profiles. The determined high temperature rate constants are k(1)(769-1307 K) = (7.1 +/- 2.7) x 10(12) cm(3) mol(-1) s(-1) and k(2)(804-1186 K) = (3.3 +/- 1.8) x 10(13) cm(3) mol(-1) s(-1). The room temperature values were found to be in very good agreement with existing literature data and show that both reactions are essentially temperature independent. The weak temperature dependence of can be explained by the interplay of a dominating direct abstraction pathway and a complex-forming mechanism. Both pathways yield the products HNO + CO. In contrast to , no evidence for a significant contribution of a direct high temperature abstraction channel was found for . Here, the observed temperature independent overall rate constant can be described by a complex-forming mechanism with several product channels. Detailed information on the strongly temperature dependent channel branching ratios is provided. Moreover, the high temperature rate constant of , OH + (CHO)(2), has been determined to be k(7) approximately 1.1 x 10(13) cm(3) mol(-1) s(-1).
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Affiliation(s)
- J Dammeier
- Institut für Physikalische Chemie, Olshausenstrasse 40, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
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