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A. R. Ravishankara - One of the best experts on this subject based on the ideXlab platform.

  • Overtone dissociation of Peroxynitric Acid (HO2NO2): absorption cross sections and photolysis products.
    The Journal of Physical Chemistry A, 2008
    Co-Authors: Harald Stark, Steven S. Brown, James B. Burkholder, Mattias Aldener, Véronique Riffault, Tomasz Gierczak, A. R. Ravishankara
    Abstract:

    Band strengths for the second (3νOH) and third (4νOH) overtones of the OH stretch vibration of Peroxynitric Acid, HO2NO2 (PNA) in the gas-phase were measured using Cavity Ring-Down Spectroscopy (CRDS). Both OH overtone transitions show diffuse smoothly varying symmetrical absorption profiles without observable rotational structure. Integrated band strengths (base e) at 296 K were determined to be S3νOH = (5.7 ± 1.1) × 10−20 and S4νOH = (4.9 ± 0.9) × 10−21 cm2 molecule−1 cm−1 with peak cross sections of (8.8 ± 1.7) × 10−22 and (7.0 ± 1.3) × 10−23 cm2 molecule−1 at 10086.0 ± 0.2 cm−1 and 13095.8 ± 0.4 cm−1, respectively, using PNA concentrations measured on line by Fourier-transform infrared and ultraviolet absorption spectroscopy. The quoted uncertainties are 2σ (95% confidence level) and include estimated systematic errors in the measurements. OH overtone spectra measured at lower temperature, 231 K, showed a narrowing of the 3νOH band along with an increase in its peak absorption cross section, but no ch...

  • Thermal decomposition of HO2NO2 (Peroxynitric Acid, PNA): rate coefficient and determination of the enthalpy of formation.
    The Journal of Physical Chemistry A, 2005
    Co-Authors: Tomasz Gierczak, James B. Burkholder, Véronique Riffault, Elena Jiménez, A. R. Ravishankara
    Abstract:

    Rate coefficients for the gas-phase thermal decomposition of HO2NO2 (Peroxynitric Acid, PNA) are reported at temperatures between 331 and 350 K at total pressures of 25 and 50 Torr of N2. Rate coefficients were determined by measuring the steady-state OH concentration in a mixture of known concentrations of HO2NO2 and NO. The measured thermal decomposition rate coefficients k-1(T,P) are used in combination with previously published rate coefficient data for the HO2NO2 formation reaction to yield a standard enthalpy for reaction 1 of ΔrH°298 K = −24.0 ± 0.5 kcal mol-1 (uncertainties are 2σ values and include estimated systematic errors). A HO2NO2 standard heat of formation, ΔfH°298 K(HO2NO2), of −12.6 ± 1.0 kcal mol-1 was calculated from this value. Some of the previously reported data on the thermal decomposition of HO2NO2 have been reanalyzed and shown to be in good agreement with our reported value.

  • Quantum yields of OH, HO2 and NO3 in the UV photolysis of HO2NO2
    Phys. Chem. Chem. Phys., 2005
    Co-Authors: Elena Jiménez, Harald Stark, James B. Burkholder, Tomasz Gierczak, A. R. Ravishankara
    Abstract:

    Quantum yields, Φ, of OH and HO2 in the ultraviolet photolysis of HO2NO2 (Peroxynitric Acid, PNA) at 193 and 248 nm and that of NO3 at 193, 248 and 308 nm are reported. Quantum yields were measured using pulsed excimer laser photolysis combined with pulsed laser induced fluorescence (PLIF) detection of OH radicals and cavity ring-down (CRD) detection of NO3 radicals. HO2 radicals were quantified by converting them to OH via the HO2 + NO → OH + NO2 reaction and detecting OH. The quantum yields obtained at 296 K are: Φ193 nm(OH) = 0.21 ± 0.12, Φ248 nm(OH) = 0.085 ± 0.08, Φ193 nm(HO2) = 0.56 ± 0.09, Φ248 nm(HO2) = 0.89 ± 0.26, Φ193 nm(NO3) = 0.35 ± 0.09, Φ248 nm(NO3) = 0.08 ± 0.04 and Φ308 nm(NO3) = 0.05 ± 0.02. The quoted uncertainties are 2σ (95% confidence level) and include estimated systematic errors. Our results are compared with the previous quantum yield measurements of OH (MacLeod et al., J. Geophys. Res., 1988, 93, 3813) and NO2 (Roehl et al., 2001, J. Phys. Chem., 105, 1592) at 248 nm and the discrepancies are discussed. The rate coefficients at 298 K for reactions of OH with HO2NO2, H2O2, HNO3 and NO are also reported.

  • reaction of oh with ho2no2 Peroxynitric Acid rate coefficients between 218 and 335 k and product yields at 298 k
    Journal of Physical Chemistry A, 2004
    Co-Authors: Elena Jiménez, James B. Burkholder, Tomasz Gierczak, H Stark, A. R. Ravishankara
    Abstract:

    Rate coefficients (k 3 (T)) for the reaction of OH with HO 2 NO 2 (Peroxynitric Acid, PNA) in the gas phase were measured in the temperature range of 218-335 K by producing OH via pulsed laser photolysis and detecting it via laser-induced fluorescence. The PNA concentration was measured in situ by UV and IR absorption. The H 2 O 2 , HNO 3 , and NO 2 impurities present in the PNA sample were quantified by mass spectrometry and/or UV/IR absorption. The measured value of k 3 (298 K) is (3.4 ′ 1.0) x 10 - 1 2 cm 3 molecule - 1 s - 1 . The temperature dependence of k 3 is best described by the relation k 3 (T) = (8.8 ′ 2.6) × 10 - 1 9 T 2 exp[(1130 ′ 20)/T] cm 3 molecule - 1 s - 1 . The quoted errors for k 3 are at the 2σ level and include estimated systematic errors, which contribute the most to this uncertainty. The measured values of k 3 (T) were independent of pressure between 10 and 100 Torr of helium. The branching ratios of the reaction OH + HO 2 NO 2 → products, for the production of HO 2 and HNO 3 and of NO 3 and H 2 O 2 , respectively, were determined to be <10% and <5%, respectively, at 298 K. Thus, it was deduced that the main pathway for reaction 3 produces H 2 O, O 2 , and NO 2 at 298 K. Our measurements reduce the uncertainties but do not significantly alter the currently calculated impacts of HO 2 NO 2 in the upper troposphere and lower stratosphere. In the course of this study, the rate coefficient for the reaction of OH with H 2 O 2 was measured to be k 4 (T) = (2.9 ′ 1.8) × 10 - 1 2 exp[-(110 ′ 150)/T] cm 3 molecule - 1 s - 1 in the temperature range of 273-356 K.

  • Reaction of OH with HO2NO2 (Peroxynitric Acid): Rate Coefficients between 218 and 335 K and Product Yields at 298 K
    The Journal of Physical Chemistry A, 2004
    Co-Authors: Elena Jiménez, Harald Stark, James B. Burkholder, Tomasz Gierczak, A. R. Ravishankara
    Abstract:

    Rate coefficients (k 3 (T)) for the reaction of OH with HO 2 NO 2 (Peroxynitric Acid, PNA) in the gas phase were measured in the temperature range of 218-335 K by producing OH via pulsed laser photolysis and detecting it via laser-induced fluorescence. The PNA concentration was measured in situ by UV and IR absorption. The H 2 O 2 , HNO 3 , and NO 2 impurities present in the PNA sample were quantified by mass spectrometry and/or UV/IR absorption. The measured value of k 3 (298 K) is (3.4 ′ 1.0) x 10 - 1 2 cm 3 molecule - 1 s - 1 . The temperature dependence of k 3 is best described by the relation k 3 (T) = (8.8 ′ 2.6) × 10 - 1 9 T 2 exp[(1130 ′ 20)/T] cm 3 molecule - 1 s - 1 . The quoted errors for k 3 are at the 2σ level and include estimated systematic errors, which contribute the most to this uncertainty. The measured values of k 3 (T) were independent of pressure between 10 and 100 Torr of helium. The branching ratios of the reaction OH + HO 2 NO 2 → products, for the production of HO 2 and HNO 3 and of NO 3 and H 2 O 2 , respectively, were determined to be

R C Cohen - One of the best experts on this subject based on the ideXlab platform.

  • Measurements of the sum of HO2NO2 and CH3O2NO2 in the remote troposphere
    Atmospheric Chemistry and Physics, 2004
    Co-Authors: J G Murphy, R. S. Rosen, C. Cantrell, Barry Lefer, Paul J. Wooldridge, Richard E. Shetter, J A Thornton, D. A. Day, R C Cohen
    Abstract:

    The chemistry of Peroxynitric Acid (HO2NO2) and methyl peroxynitrate (CH3O2NO2)is predicted to be particularly important in the upper troposphere where temperatures are frequently low enough that these compounds do not rapidly decompose. At temperatures below 240K, we calculate that about 20% of NOy in the mid- and high-latitude upper troposphere is HO2NO2. Under these conditions, the reaction of OH with HO2NO2 is estimated to account for as much as one third of the permanent loss of hydrogen radicals. During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign, we used thermal dissociation laser-induced fluorescence (TD-LIF) to measure the sum of peroxynitrates (PNs HO2NO2+CH3O2NO2+PAN+PPN+...) aboard the NCAR C-130 research aircraft. We infer the sum of HO2NO2 and CH3O2NO2 as the difference between PN measurements and gas chromatographic measurements of the two major peroxy acyl nitrates, peroxy acetyl nitrate (PAN) and peroxy propionyl nitrate (PPN). Comparison with NOy and other nitrogen oxide measurements confirms the importance of HO2NO2 and CH3O2NO2 to the reactive nitrogen budget and shows that current thinking about the chemistry of these species is approximately correct. During the spring high latitude conditions sampled during the TOPSE experiment, the model predictions of the contribution of (HO2NO2+CH3O2NO2) to NOy are highly temperature dependent: on average 30% of NOy at 230K, 15% of NOy at 240K, and 5% of NOy above 250K. The temperature dependence of the inferred concentrations corroborates the contribution of overtone photolysis to the photochemistry of Peroxynitric Acid. A model that includes IR photolysis (J=1x10-5s-1) agreed with the observed sum of HO2NO2+CH3O2NO2 to better than 35% below 240K where the concentration of these species is largest.

  • Measurements of the sum of HO2NO2 and CH3O2NO2 in the remote troposphere - eScholarship
    2004
    Co-Authors: J G Murphy, R. S. Rosen, Barry Lefer, Paul J. Wooldridge, Christopher A. Cantrell, Richard E. Shetter, J A Thornton, R C Cohen
    Abstract:

    The chemistry of Peroxynitric Acid (HO2NO2) and methyl peroxynitrate (CH3O2NO2) is predicted to be particularly important in the upper troposphere where temperatures are frequently low enough that these compounds do not rapidly decompose. At temperatures below 240 K, we calculate that about 20% of NOy in the mid- and high-latitude upper troposphere is HO2NO2. Under these conditions, the reaction of OH with HO2NO2 is estimated to account for as much as one third of the permanent loss of hydrogen radicals. During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign, we used thermal dissociation laser-induced fluorescence (TD-LIF) to measure the sum of peroxynitrates (SigmaPNsequivalent toHO(2)NO(2)+CH3O2NO2+PAN+PPN+...) aboard the NCAR C-130 research aircraft. We infer the sum of HO2NO2 and CH3O2NO2 as the difference between SigmaPN measurements and gas chromatographic measurements of the two major peroxy acyl nitrates, peroxy acetyl nitrate (PAN) and peroxy propionyl nitrate (PPN). Comparison with NOy and other nitrogen oxide measurements confirms the importance of HO2NO2 and CH3O2NO2 to the reactive nitrogen budget and shows that current thinking about the chemistry of these species is approximately correct. During the spring high latitude conditions sampled during the TOPSE experiment, the model predictions of the contribution of (HO2NO2+CH3O2NO2) to NOy are highly temperature dependent: on average 30% of NOy at 230 K, 15% of NOy at 240 K, and

  • Measurements of the sum of HO<sub>2</sub>NO<sub>2</sub> and CH<sub>3</sub>O<sub>2</sub>NO<sub>2</sub> in the remote troposphere
    Atmospheric Chemistry and Physics Discussions, 2003
    Co-Authors: J G Murphy, R. S. Rosen, C. Cantrell, Barry Lefer, Paul J. Wooldridge, Richard E. Shetter, J A Thornton, R C Cohen
    Abstract:

    Abstract. The chemistry of Peroxynitric Acid (HO2NO2) and methyl peroxynitrate (CH3O2NO2) is predicted to be particularly important in the upper troposphere where temperatures are frequently low enough that these compounds do not rapidly decompose. At temperatures below 240 K, we calculate that about 20% of NOy in the mid and polar latitude upper troposphere is HO2NO2. Under these conditions, the reaction of OH with HO2NO2 is estimated to account for as much as one third of the permanent loss of hydrogen radicals. During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign, we used thermal dissociation laser-induced fluorescence (TD-LIF) to measure the sum of peroxynitrates (SPNs equivanlent HO2NO2 + CH3O2NO2 + PAN + PPN + ...), aboard the NCAR C-130 research aircraft. We infer the sum of HO2NO2 and CH3O2NO2 as the difference between SPN measurements and gas chromatographic measurements of the two major peroxy acyl nitrates, peroxy acetyl nitrate (PAN) and peroxy propionyl nitrate (PPN). Comparison with NOy and other nitrogen oxide measurements confirms the importance of HO2NO2 and CH3O2NO2 to the reactive nitrogen budget and shows that current thinking about the chemistry of these species is approximately correct. The temperature dependence of the inferred concentrations corroborates the contribution of overtone photolysis to the photochemistry of Peroxynitric Acid.

  • Measurements of the sum of HO 2 NO 2 and CH 3 O 2 NO 2 in the remote troposphere
    Atmospheric Chemistry and Physics, 2003
    Co-Authors: J G Murphy, R. S. Rosen, Barry Lefer, Paul J. Wooldridge, Christopher A. Cantrell, Richard E. Shetter, J A Thornton, R C Cohen
    Abstract:

    The chemistry of Peroxynitric Acid (HO2NO2) and methyl peroxynitrate (CH3O2NO2) is predicted to be particularly important in the upper troposphere where tem- peratures are frequently low enough that these compounds do not rapidly decompose. At temperatures below 240 K, we calculate that about 20% of NOy in the mid- and high-latitude upper troposphere is HO2NO2. Under these conditions, the reaction of OH with HO2NO2 is esti- mated to account for as much as one third of the perma- nent loss of hydrogen radicals. During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) cam- paign, we used thermal dissociation laser-induced fluo- rescence (TD-LIF) to measure the sum of peroxynitrates (6PNs HO2NO2+CH3O2NO2+PAN+PPN+. . . ) aboard the NCAR C-130 research aircraft. We infer the sum of HO2NO2 and CH3O2NO2 as the difference between 6PN measurements and gas chromatographic measurements of the two major peroxy acyl nitrates, peroxy acetyl nitrate (PAN) and peroxy propionyl nitrate (PPN). Comparison with NOy and other nitrogen oxide measurements confirms the im- portance of HO2NO2 and CH3O2NO2 to the reactive ni- trogen budget and shows that current thinking about the chemistry of these species is approximately correct. Dur- ing the spring high latitude conditions sampled during the TOPSE experiment, the model predictions of the contribu- tion of (HO2NO2+CH3O2NO2) to NOy are highly temper- ature dependent: on average 30% of NOy at 230 K, 15% of NOy at 240 K, and

  • Measurements of the sum of HO2NO2 and CH3O2NO2 in the remote troposphere
    Atmospheric Chemistry and Physics Discussions, 2003
    Co-Authors: J G Murphy, R. S. Rosen, C. Cantrell, Barry Lefer, Paul J. Wooldridge, Richard E. Shetter, J A Thornton, D. A. Day, R C Cohen
    Abstract:

    The chemistry of Peroxynitric Acid (HO2NO2) and methyl peroxynitrate (CH3O2NO2) is predicted to be particularly important in the upper troposphere where temperatures are frequently low enough that these compounds do not rapidly decompose. At temperatures below 240 K, we calculate that about 20% of NOy in the mid and polar latitude upper troposphere is HO2NO2. Under these conditions, the reaction of OH with HO2NO2 is estimated to account for as much as one third of the permanent loss of hydrogen radicals. During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign, we used thermal dissociation laser-induced fluorescence (TD-LIF) to measure the sum of peroxynitrates (SPNs equivanlent HO2NO2 + CH3O2NO2 + PAN + PPN + ...), aboard the NCAR C-130 research aircraft. We infer the sum of HO2NO2 and CH3O2NO2 as the difference between SPN measurements and gas chromatographic measurements of the two major peroxy acyl nitrates, peroxy acetyl nitrate (PAN) and peroxy propionyl nitrate (PPN). Comparison with NOy and other nitrogen oxide measurements confirms the importance of HO2NO2 and CH3O2NO2 to the reactive nitrogen budget and shows that current thinking about the chemistry of these species is approximately correct. The temperature dependence of the inferred concentrations corroborates the contribution of overtone photolysis to the photochemistry of Peroxynitric Acid.

J G Murphy - One of the best experts on this subject based on the ideXlab platform.

  • Measurements of the sum of HO2NO2 and CH3O2NO2 in the remote troposphere
    Atmospheric Chemistry and Physics, 2004
    Co-Authors: J G Murphy, R. S. Rosen, C. Cantrell, Barry Lefer, Paul J. Wooldridge, Richard E. Shetter, J A Thornton, D. A. Day, R C Cohen
    Abstract:

    The chemistry of Peroxynitric Acid (HO2NO2) and methyl peroxynitrate (CH3O2NO2)is predicted to be particularly important in the upper troposphere where temperatures are frequently low enough that these compounds do not rapidly decompose. At temperatures below 240K, we calculate that about 20% of NOy in the mid- and high-latitude upper troposphere is HO2NO2. Under these conditions, the reaction of OH with HO2NO2 is estimated to account for as much as one third of the permanent loss of hydrogen radicals. During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign, we used thermal dissociation laser-induced fluorescence (TD-LIF) to measure the sum of peroxynitrates (PNs HO2NO2+CH3O2NO2+PAN+PPN+...) aboard the NCAR C-130 research aircraft. We infer the sum of HO2NO2 and CH3O2NO2 as the difference between PN measurements and gas chromatographic measurements of the two major peroxy acyl nitrates, peroxy acetyl nitrate (PAN) and peroxy propionyl nitrate (PPN). Comparison with NOy and other nitrogen oxide measurements confirms the importance of HO2NO2 and CH3O2NO2 to the reactive nitrogen budget and shows that current thinking about the chemistry of these species is approximately correct. During the spring high latitude conditions sampled during the TOPSE experiment, the model predictions of the contribution of (HO2NO2+CH3O2NO2) to NOy are highly temperature dependent: on average 30% of NOy at 230K, 15% of NOy at 240K, and 5% of NOy above 250K. The temperature dependence of the inferred concentrations corroborates the contribution of overtone photolysis to the photochemistry of Peroxynitric Acid. A model that includes IR photolysis (J=1x10-5s-1) agreed with the observed sum of HO2NO2+CH3O2NO2 to better than 35% below 240K where the concentration of these species is largest.

  • Measurements of the sum of HO2NO2 and CH3O2NO2 in the remote troposphere - eScholarship
    2004
    Co-Authors: J G Murphy, R. S. Rosen, Barry Lefer, Paul J. Wooldridge, Christopher A. Cantrell, Richard E. Shetter, J A Thornton, R C Cohen
    Abstract:

    The chemistry of Peroxynitric Acid (HO2NO2) and methyl peroxynitrate (CH3O2NO2) is predicted to be particularly important in the upper troposphere where temperatures are frequently low enough that these compounds do not rapidly decompose. At temperatures below 240 K, we calculate that about 20% of NOy in the mid- and high-latitude upper troposphere is HO2NO2. Under these conditions, the reaction of OH with HO2NO2 is estimated to account for as much as one third of the permanent loss of hydrogen radicals. During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign, we used thermal dissociation laser-induced fluorescence (TD-LIF) to measure the sum of peroxynitrates (SigmaPNsequivalent toHO(2)NO(2)+CH3O2NO2+PAN+PPN+...) aboard the NCAR C-130 research aircraft. We infer the sum of HO2NO2 and CH3O2NO2 as the difference between SigmaPN measurements and gas chromatographic measurements of the two major peroxy acyl nitrates, peroxy acetyl nitrate (PAN) and peroxy propionyl nitrate (PPN). Comparison with NOy and other nitrogen oxide measurements confirms the importance of HO2NO2 and CH3O2NO2 to the reactive nitrogen budget and shows that current thinking about the chemistry of these species is approximately correct. During the spring high latitude conditions sampled during the TOPSE experiment, the model predictions of the contribution of (HO2NO2+CH3O2NO2) to NOy are highly temperature dependent: on average 30% of NOy at 230 K, 15% of NOy at 240 K, and

  • Measurements of the sum of HO<sub>2</sub>NO<sub>2</sub> and CH<sub>3</sub>O<sub>2</sub>NO<sub>2</sub> in the remote troposphere
    Atmospheric Chemistry and Physics Discussions, 2003
    Co-Authors: J G Murphy, R. S. Rosen, C. Cantrell, Barry Lefer, Paul J. Wooldridge, Richard E. Shetter, J A Thornton, R C Cohen
    Abstract:

    Abstract. The chemistry of Peroxynitric Acid (HO2NO2) and methyl peroxynitrate (CH3O2NO2) is predicted to be particularly important in the upper troposphere where temperatures are frequently low enough that these compounds do not rapidly decompose. At temperatures below 240 K, we calculate that about 20% of NOy in the mid and polar latitude upper troposphere is HO2NO2. Under these conditions, the reaction of OH with HO2NO2 is estimated to account for as much as one third of the permanent loss of hydrogen radicals. During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign, we used thermal dissociation laser-induced fluorescence (TD-LIF) to measure the sum of peroxynitrates (SPNs equivanlent HO2NO2 + CH3O2NO2 + PAN + PPN + ...), aboard the NCAR C-130 research aircraft. We infer the sum of HO2NO2 and CH3O2NO2 as the difference between SPN measurements and gas chromatographic measurements of the two major peroxy acyl nitrates, peroxy acetyl nitrate (PAN) and peroxy propionyl nitrate (PPN). Comparison with NOy and other nitrogen oxide measurements confirms the importance of HO2NO2 and CH3O2NO2 to the reactive nitrogen budget and shows that current thinking about the chemistry of these species is approximately correct. The temperature dependence of the inferred concentrations corroborates the contribution of overtone photolysis to the photochemistry of Peroxynitric Acid.

  • Measurements of the sum of HO 2 NO 2 and CH 3 O 2 NO 2 in the remote troposphere
    Atmospheric Chemistry and Physics, 2003
    Co-Authors: J G Murphy, R. S. Rosen, Barry Lefer, Paul J. Wooldridge, Christopher A. Cantrell, Richard E. Shetter, J A Thornton, R C Cohen
    Abstract:

    The chemistry of Peroxynitric Acid (HO2NO2) and methyl peroxynitrate (CH3O2NO2) is predicted to be particularly important in the upper troposphere where tem- peratures are frequently low enough that these compounds do not rapidly decompose. At temperatures below 240 K, we calculate that about 20% of NOy in the mid- and high-latitude upper troposphere is HO2NO2. Under these conditions, the reaction of OH with HO2NO2 is esti- mated to account for as much as one third of the perma- nent loss of hydrogen radicals. During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) cam- paign, we used thermal dissociation laser-induced fluo- rescence (TD-LIF) to measure the sum of peroxynitrates (6PNs HO2NO2+CH3O2NO2+PAN+PPN+. . . ) aboard the NCAR C-130 research aircraft. We infer the sum of HO2NO2 and CH3O2NO2 as the difference between 6PN measurements and gas chromatographic measurements of the two major peroxy acyl nitrates, peroxy acetyl nitrate (PAN) and peroxy propionyl nitrate (PPN). Comparison with NOy and other nitrogen oxide measurements confirms the im- portance of HO2NO2 and CH3O2NO2 to the reactive ni- trogen budget and shows that current thinking about the chemistry of these species is approximately correct. Dur- ing the spring high latitude conditions sampled during the TOPSE experiment, the model predictions of the contribu- tion of (HO2NO2+CH3O2NO2) to NOy are highly temper- ature dependent: on average 30% of NOy at 230 K, 15% of NOy at 240 K, and

  • Measurements of the sum of HO2NO2 and CH3O2NO2 in the remote troposphere
    Atmospheric Chemistry and Physics Discussions, 2003
    Co-Authors: J G Murphy, R. S. Rosen, C. Cantrell, Barry Lefer, Paul J. Wooldridge, Richard E. Shetter, J A Thornton, D. A. Day, R C Cohen
    Abstract:

    The chemistry of Peroxynitric Acid (HO2NO2) and methyl peroxynitrate (CH3O2NO2) is predicted to be particularly important in the upper troposphere where temperatures are frequently low enough that these compounds do not rapidly decompose. At temperatures below 240 K, we calculate that about 20% of NOy in the mid and polar latitude upper troposphere is HO2NO2. Under these conditions, the reaction of OH with HO2NO2 is estimated to account for as much as one third of the permanent loss of hydrogen radicals. During the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign, we used thermal dissociation laser-induced fluorescence (TD-LIF) to measure the sum of peroxynitrates (SPNs equivanlent HO2NO2 + CH3O2NO2 + PAN + PPN + ...), aboard the NCAR C-130 research aircraft. We infer the sum of HO2NO2 and CH3O2NO2 as the difference between SPN measurements and gas chromatographic measurements of the two major peroxy acyl nitrates, peroxy acetyl nitrate (PAN) and peroxy propionyl nitrate (PPN). Comparison with NOy and other nitrogen oxide measurements confirms the importance of HO2NO2 and CH3O2NO2 to the reactive nitrogen budget and shows that current thinking about the chemistry of these species is approximately correct. The temperature dependence of the inferred concentrations corroborates the contribution of overtone photolysis to the photochemistry of Peroxynitric Acid.

Elena Jiménez - One of the best experts on this subject based on the ideXlab platform.

  • Thermal decomposition of HO2NO2 (Peroxynitric Acid, PNA): rate coefficient and determination of the enthalpy of formation.
    The Journal of Physical Chemistry A, 2005
    Co-Authors: Tomasz Gierczak, James B. Burkholder, Véronique Riffault, Elena Jiménez, A. R. Ravishankara
    Abstract:

    Rate coefficients for the gas-phase thermal decomposition of HO2NO2 (Peroxynitric Acid, PNA) are reported at temperatures between 331 and 350 K at total pressures of 25 and 50 Torr of N2. Rate coefficients were determined by measuring the steady-state OH concentration in a mixture of known concentrations of HO2NO2 and NO. The measured thermal decomposition rate coefficients k-1(T,P) are used in combination with previously published rate coefficient data for the HO2NO2 formation reaction to yield a standard enthalpy for reaction 1 of ΔrH°298 K = −24.0 ± 0.5 kcal mol-1 (uncertainties are 2σ values and include estimated systematic errors). A HO2NO2 standard heat of formation, ΔfH°298 K(HO2NO2), of −12.6 ± 1.0 kcal mol-1 was calculated from this value. Some of the previously reported data on the thermal decomposition of HO2NO2 have been reanalyzed and shown to be in good agreement with our reported value.

  • Quantum yields of OH, HO2 and NO3 in the UV photolysis of HO2NO2
    Phys. Chem. Chem. Phys., 2005
    Co-Authors: Elena Jiménez, Harald Stark, James B. Burkholder, Tomasz Gierczak, A. R. Ravishankara
    Abstract:

    Quantum yields, Φ, of OH and HO2 in the ultraviolet photolysis of HO2NO2 (Peroxynitric Acid, PNA) at 193 and 248 nm and that of NO3 at 193, 248 and 308 nm are reported. Quantum yields were measured using pulsed excimer laser photolysis combined with pulsed laser induced fluorescence (PLIF) detection of OH radicals and cavity ring-down (CRD) detection of NO3 radicals. HO2 radicals were quantified by converting them to OH via the HO2 + NO → OH + NO2 reaction and detecting OH. The quantum yields obtained at 296 K are: Φ193 nm(OH) = 0.21 ± 0.12, Φ248 nm(OH) = 0.085 ± 0.08, Φ193 nm(HO2) = 0.56 ± 0.09, Φ248 nm(HO2) = 0.89 ± 0.26, Φ193 nm(NO3) = 0.35 ± 0.09, Φ248 nm(NO3) = 0.08 ± 0.04 and Φ308 nm(NO3) = 0.05 ± 0.02. The quoted uncertainties are 2σ (95% confidence level) and include estimated systematic errors. Our results are compared with the previous quantum yield measurements of OH (MacLeod et al., J. Geophys. Res., 1988, 93, 3813) and NO2 (Roehl et al., 2001, J. Phys. Chem., 105, 1592) at 248 nm and the discrepancies are discussed. The rate coefficients at 298 K for reactions of OH with HO2NO2, H2O2, HNO3 and NO are also reported.

  • reaction of oh with ho2no2 Peroxynitric Acid rate coefficients between 218 and 335 k and product yields at 298 k
    Journal of Physical Chemistry A, 2004
    Co-Authors: Elena Jiménez, James B. Burkholder, Tomasz Gierczak, H Stark, A. R. Ravishankara
    Abstract:

    Rate coefficients (k 3 (T)) for the reaction of OH with HO 2 NO 2 (Peroxynitric Acid, PNA) in the gas phase were measured in the temperature range of 218-335 K by producing OH via pulsed laser photolysis and detecting it via laser-induced fluorescence. The PNA concentration was measured in situ by UV and IR absorption. The H 2 O 2 , HNO 3 , and NO 2 impurities present in the PNA sample were quantified by mass spectrometry and/or UV/IR absorption. The measured value of k 3 (298 K) is (3.4 ′ 1.0) x 10 - 1 2 cm 3 molecule - 1 s - 1 . The temperature dependence of k 3 is best described by the relation k 3 (T) = (8.8 ′ 2.6) × 10 - 1 9 T 2 exp[(1130 ′ 20)/T] cm 3 molecule - 1 s - 1 . The quoted errors for k 3 are at the 2σ level and include estimated systematic errors, which contribute the most to this uncertainty. The measured values of k 3 (T) were independent of pressure between 10 and 100 Torr of helium. The branching ratios of the reaction OH + HO 2 NO 2 → products, for the production of HO 2 and HNO 3 and of NO 3 and H 2 O 2 , respectively, were determined to be <10% and <5%, respectively, at 298 K. Thus, it was deduced that the main pathway for reaction 3 produces H 2 O, O 2 , and NO 2 at 298 K. Our measurements reduce the uncertainties but do not significantly alter the currently calculated impacts of HO 2 NO 2 in the upper troposphere and lower stratosphere. In the course of this study, the rate coefficient for the reaction of OH with H 2 O 2 was measured to be k 4 (T) = (2.9 ′ 1.8) × 10 - 1 2 exp[-(110 ′ 150)/T] cm 3 molecule - 1 s - 1 in the temperature range of 273-356 K.

  • Reaction of OH with HO2NO2 (Peroxynitric Acid): Rate Coefficients between 218 and 335 K and Product Yields at 298 K
    The Journal of Physical Chemistry A, 2004
    Co-Authors: Elena Jiménez, Harald Stark, James B. Burkholder, Tomasz Gierczak, A. R. Ravishankara
    Abstract:

    Rate coefficients (k 3 (T)) for the reaction of OH with HO 2 NO 2 (Peroxynitric Acid, PNA) in the gas phase were measured in the temperature range of 218-335 K by producing OH via pulsed laser photolysis and detecting it via laser-induced fluorescence. The PNA concentration was measured in situ by UV and IR absorption. The H 2 O 2 , HNO 3 , and NO 2 impurities present in the PNA sample were quantified by mass spectrometry and/or UV/IR absorption. The measured value of k 3 (298 K) is (3.4 ′ 1.0) x 10 - 1 2 cm 3 molecule - 1 s - 1 . The temperature dependence of k 3 is best described by the relation k 3 (T) = (8.8 ′ 2.6) × 10 - 1 9 T 2 exp[(1130 ′ 20)/T] cm 3 molecule - 1 s - 1 . The quoted errors for k 3 are at the 2σ level and include estimated systematic errors, which contribute the most to this uncertainty. The measured values of k 3 (T) were independent of pressure between 10 and 100 Torr of helium. The branching ratios of the reaction OH + HO 2 NO 2 → products, for the production of HO 2 and HNO 3 and of NO 3 and H 2 O 2 , respectively, were determined to be

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  • Overtone dissociation of Peroxynitric Acid (HO2NO2): absorption cross sections and photolysis products.
    The Journal of Physical Chemistry A, 2008
    Co-Authors: Harald Stark, Steven S. Brown, James B. Burkholder, Mattias Aldener, Véronique Riffault, Tomasz Gierczak, A. R. Ravishankara
    Abstract:

    Band strengths for the second (3νOH) and third (4νOH) overtones of the OH stretch vibration of Peroxynitric Acid, HO2NO2 (PNA) in the gas-phase were measured using Cavity Ring-Down Spectroscopy (CRDS). Both OH overtone transitions show diffuse smoothly varying symmetrical absorption profiles without observable rotational structure. Integrated band strengths (base e) at 296 K were determined to be S3νOH = (5.7 ± 1.1) × 10−20 and S4νOH = (4.9 ± 0.9) × 10−21 cm2 molecule−1 cm−1 with peak cross sections of (8.8 ± 1.7) × 10−22 and (7.0 ± 1.3) × 10−23 cm2 molecule−1 at 10086.0 ± 0.2 cm−1 and 13095.8 ± 0.4 cm−1, respectively, using PNA concentrations measured on line by Fourier-transform infrared and ultraviolet absorption spectroscopy. The quoted uncertainties are 2σ (95% confidence level) and include estimated systematic errors in the measurements. OH overtone spectra measured at lower temperature, 231 K, showed a narrowing of the 3νOH band along with an increase in its peak absorption cross section, but no ch...

  • Thermal decomposition of HO2NO2 (Peroxynitric Acid, PNA): rate coefficient and determination of the enthalpy of formation.
    The Journal of Physical Chemistry A, 2005
    Co-Authors: Tomasz Gierczak, James B. Burkholder, Véronique Riffault, Elena Jiménez, A. R. Ravishankara
    Abstract:

    Rate coefficients for the gas-phase thermal decomposition of HO2NO2 (Peroxynitric Acid, PNA) are reported at temperatures between 331 and 350 K at total pressures of 25 and 50 Torr of N2. Rate coefficients were determined by measuring the steady-state OH concentration in a mixture of known concentrations of HO2NO2 and NO. The measured thermal decomposition rate coefficients k-1(T,P) are used in combination with previously published rate coefficient data for the HO2NO2 formation reaction to yield a standard enthalpy for reaction 1 of ΔrH°298 K = −24.0 ± 0.5 kcal mol-1 (uncertainties are 2σ values and include estimated systematic errors). A HO2NO2 standard heat of formation, ΔfH°298 K(HO2NO2), of −12.6 ± 1.0 kcal mol-1 was calculated from this value. Some of the previously reported data on the thermal decomposition of HO2NO2 have been reanalyzed and shown to be in good agreement with our reported value.

  • Quantum yields of OH, HO2 and NO3 in the UV photolysis of HO2NO2
    Phys. Chem. Chem. Phys., 2005
    Co-Authors: Elena Jiménez, Harald Stark, James B. Burkholder, Tomasz Gierczak, A. R. Ravishankara
    Abstract:

    Quantum yields, Φ, of OH and HO2 in the ultraviolet photolysis of HO2NO2 (Peroxynitric Acid, PNA) at 193 and 248 nm and that of NO3 at 193, 248 and 308 nm are reported. Quantum yields were measured using pulsed excimer laser photolysis combined with pulsed laser induced fluorescence (PLIF) detection of OH radicals and cavity ring-down (CRD) detection of NO3 radicals. HO2 radicals were quantified by converting them to OH via the HO2 + NO → OH + NO2 reaction and detecting OH. The quantum yields obtained at 296 K are: Φ193 nm(OH) = 0.21 ± 0.12, Φ248 nm(OH) = 0.085 ± 0.08, Φ193 nm(HO2) = 0.56 ± 0.09, Φ248 nm(HO2) = 0.89 ± 0.26, Φ193 nm(NO3) = 0.35 ± 0.09, Φ248 nm(NO3) = 0.08 ± 0.04 and Φ308 nm(NO3) = 0.05 ± 0.02. The quoted uncertainties are 2σ (95% confidence level) and include estimated systematic errors. Our results are compared with the previous quantum yield measurements of OH (MacLeod et al., J. Geophys. Res., 1988, 93, 3813) and NO2 (Roehl et al., 2001, J. Phys. Chem., 105, 1592) at 248 nm and the discrepancies are discussed. The rate coefficients at 298 K for reactions of OH with HO2NO2, H2O2, HNO3 and NO are also reported.

  • reaction of oh with ho2no2 Peroxynitric Acid rate coefficients between 218 and 335 k and product yields at 298 k
    Journal of Physical Chemistry A, 2004
    Co-Authors: Elena Jiménez, James B. Burkholder, Tomasz Gierczak, H Stark, A. R. Ravishankara
    Abstract:

    Rate coefficients (k 3 (T)) for the reaction of OH with HO 2 NO 2 (Peroxynitric Acid, PNA) in the gas phase were measured in the temperature range of 218-335 K by producing OH via pulsed laser photolysis and detecting it via laser-induced fluorescence. The PNA concentration was measured in situ by UV and IR absorption. The H 2 O 2 , HNO 3 , and NO 2 impurities present in the PNA sample were quantified by mass spectrometry and/or UV/IR absorption. The measured value of k 3 (298 K) is (3.4 ′ 1.0) x 10 - 1 2 cm 3 molecule - 1 s - 1 . The temperature dependence of k 3 is best described by the relation k 3 (T) = (8.8 ′ 2.6) × 10 - 1 9 T 2 exp[(1130 ′ 20)/T] cm 3 molecule - 1 s - 1 . The quoted errors for k 3 are at the 2σ level and include estimated systematic errors, which contribute the most to this uncertainty. The measured values of k 3 (T) were independent of pressure between 10 and 100 Torr of helium. The branching ratios of the reaction OH + HO 2 NO 2 → products, for the production of HO 2 and HNO 3 and of NO 3 and H 2 O 2 , respectively, were determined to be <10% and <5%, respectively, at 298 K. Thus, it was deduced that the main pathway for reaction 3 produces H 2 O, O 2 , and NO 2 at 298 K. Our measurements reduce the uncertainties but do not significantly alter the currently calculated impacts of HO 2 NO 2 in the upper troposphere and lower stratosphere. In the course of this study, the rate coefficient for the reaction of OH with H 2 O 2 was measured to be k 4 (T) = (2.9 ′ 1.8) × 10 - 1 2 exp[-(110 ′ 150)/T] cm 3 molecule - 1 s - 1 in the temperature range of 273-356 K.

  • Reaction of OH with HO2NO2 (Peroxynitric Acid): Rate Coefficients between 218 and 335 K and Product Yields at 298 K
    The Journal of Physical Chemistry A, 2004
    Co-Authors: Elena Jiménez, Harald Stark, James B. Burkholder, Tomasz Gierczak, A. R. Ravishankara
    Abstract:

    Rate coefficients (k 3 (T)) for the reaction of OH with HO 2 NO 2 (Peroxynitric Acid, PNA) in the gas phase were measured in the temperature range of 218-335 K by producing OH via pulsed laser photolysis and detecting it via laser-induced fluorescence. The PNA concentration was measured in situ by UV and IR absorption. The H 2 O 2 , HNO 3 , and NO 2 impurities present in the PNA sample were quantified by mass spectrometry and/or UV/IR absorption. The measured value of k 3 (298 K) is (3.4 ′ 1.0) x 10 - 1 2 cm 3 molecule - 1 s - 1 . The temperature dependence of k 3 is best described by the relation k 3 (T) = (8.8 ′ 2.6) × 10 - 1 9 T 2 exp[(1130 ′ 20)/T] cm 3 molecule - 1 s - 1 . The quoted errors for k 3 are at the 2σ level and include estimated systematic errors, which contribute the most to this uncertainty. The measured values of k 3 (T) were independent of pressure between 10 and 100 Torr of helium. The branching ratios of the reaction OH + HO 2 NO 2 → products, for the production of HO 2 and HNO 3 and of NO 3 and H 2 O 2 , respectively, were determined to be