Bromine Nitrate Photochemistry:  Quantum Yields for O, Br, and BrO Over the Wavelength Range 248−355 nm

Soller, Raenell; Nicovich, J. M.; Wine, P. H.

doi:10.1021/jp020018r

Cited by 14 publications

(10 citation statements)

References 29 publications

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“…The uncertainty of σ (BrONO 2 ) is due to its large decrease by 3.5 orders of magnitude with wavelength, when going from the extreme UV (λ = 200 nm) to λ > 300 nm, where the actinic fluxes, and thus the spectral contribution to J(BrONO 2 ), strongly increase. BrONO 2 can also be destroyed by the reaction (Soller et al, 2002) BrONO 2 + O( 3 P) −→ BrO + NO 3 .…”

Section: S Kreycy Et Al: In Situ Test Of the J(brono 2 )/K Bro+no 2mentioning

confidence: 99%

Atmospheric test of the J(BrONO2)/kBrO+NO2 ratio: implications for total stratospheric Bry and bromine-mediated ozone loss

et al. 2013

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Abstract. We report on time-dependent O3, NO2 and BrO profiles measured by limb observations of scattered skylight in the stratosphere over Kiruna (67.9° N, 22.1° E) on 7 and 8 September 2009 during the autumn circulation turn-over. The observations are complemented by simultaneous direct solar occultation measurements around sunset and sunrise performed aboard the same stratospheric balloon payload. Supporting radiative transfer and photochemical modelling indicate that the measurements can be used to constrain the ratio J(BrONO2)/kBrO+NO2, for which at T = 220 ± 5 K an overall 1.7 (+0.4 −0.2) larger ratio is found than recommended by the most recent Jet Propulsion Laboratory (JPL) compilation (Sander et al., 2011). Sensitivity studies reveal the major reasons are likely to be (1) a larger BrONO2 absorption cross-section σBrONO2, primarily for wavelengths larger than 300 nm, and (2) a smaller kBrO+NO2 at 220 K than given by Sander et al. (2011). Other factors, e.g. the actinic flux and quantum yield for the dissociation of BrONO2, can be ruled out. The observations also have consequences for total inorganic stratospheric bromine (Bry) estimated from stratospheric BrO measurements at high NOx loadings, since the ratio J(BrONO2)/kBrO+NO2 largely determines the stratospheric BrO/Bry ratio during daylight. Using the revised J(BrONO2)/kBrO+NO2 ratio, total stratospheric Bry is likely to be 1.4 ppt smaller than previously estimated from BrO profile measurements at high NOx loadings. This would bring estimates of Bry inferred from organic source gas measurements (e.g. CH3Br, the halons, CH2Br2, CHBr3, etc.) into closer agreement with estimates based on BrO observations (inorganic method). The consequences for stratospheric ozone due to the revised J(BrONO2)/kBrO+NO2 ratio are small (maximum −0.8%), since at high NOx (for which most Bry assessments are made) the enhanced ozone loss by overestimating Bry is compensated for by the suppressed ozone loss due to the underestimation of BrO/Bry with a smaller J(BrONO2)/kBrO+NO2 ratio.

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Section: S Kreycy Et Al: In Situ Test Of the J(brono 2 )/K Bro+no 2mentioning

confidence: 99%

Atmospheric test of the J(BrONO2)/kBrO+NO2 ratio: implications for total stratospheric Bry and bromine-mediated ozone loss

et al. 2013

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“…Harwood et al 7 measured photodissociation quantum yields for the production of NO 3 from BrONO 2 at wavelengths of 248, 308, and 352.5 nm. More recently, Soller et al 8 have reported quantum yields of Br, O, and BrO from photodissociation of BrONO 2 at wavelengths from 248 to 355 nm. No measurement of quantum yields has been reported for wavelengths longer than 360 nm.…”

Section: Introductionmentioning

confidence: 99%

The role of triplet states in the long wavelength absorption region of bromine nitrate

Peterson

Francisco

et al. 2003

The Journal of Chemical Physics

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Articles you may be interested inAn ab initio investigation of the ground and low-lying singlet and triplet electronic states of XNO2 and XONO (X = Cl, Br, and I)The electronic states of pyridine-N-oxide studied by VUV photoabsorption and ab initio configuration interaction computations J. Chem. Phys. 138, 214317 (2013); 10.1063/1.4807841Computational studies on the ground and excited states of BrOOBr A theoretical study of the low-lying singlet and triplet electronic states of BrONO 2 is presented. Calculations of excitation energies and oscillator strengths are reported using excited-state coupled cluster response methods, as well as the complete active space self-consistent field method with the full Breit-Pauli spin-orbit operator. The calculations predict that there is only one singlet state for BrONO 2 , the Ã 1 AЉ state, that is accessible at wavelengths longer than 300 nm. At energies below the first singlet state, i.e., Ͼ330 nm, the calculations reveal two triplet states with significant oscillator strength. Therefore, we propose that the origin of absorption in the long wavelength region from 350 to 500 nm, responsible for the majority of atmospheric photolysis, is due to transitions to triplet states and not singlet states. A comparison of the reported benchmark coupled cluster calculations ͑CCSD͒ with the results of ͑1͒ configuration interaction with all single substitutions and a perturbative correction for the double substitutions ͓CIS͑D͔͒ and ͑2͒ time-dependent density-functional ͑TDDF͒ calculations is provided. For the lowest energy excitations, CIS͑D͒ calculations provide quantitative agreement with the CCSD results, while TDDF calculations yield qualitative agreement.

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“…The experimental apparatus used in this study is similar to that employed in previous studies carried out in our laboratory where loss or production of atomic bromine was monitored using the RF technique. − The experimental approach involves coupling the time-resolved RF detection scheme with production of Br by LFP of CF 2 Br 2 . A schematic diagram of the LFP–RF apparatus is published elsewhere .…”

Section: Methodsmentioning

confidence: 99%

Kinetics of Elementary Steps in the Reactions of Atomic Bromine with Isoprene and 1,3-Butadiene under Atmospheric Conditions

Laine¹,

Sohn²,

Nicovich³

et al. 2012

J. Phys. Chem. A

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Laser flash photolysis of CF(2)Br(2) has been coupled with time-resolved detection of atomic bromine by resonance fluorescence spectroscopy to investigate the gas-phase kinetics of early elementary steps in the Br-initiated oxidations of isoprene (2-methyl-1,3-butadiene, Iso) and 1,3-butadiene (Bu) under atmospheric conditions. At T ≥ 526 K, measured rate coefficients for Br + isoprene are independent of pressure, suggesting that hydrogen transfer (1a) is the dominant reaction pathway. The following Arrhenius expression adequately describes all kinetic data at 526 K ≤ T ≤ 673 K: k(1a)(T) = (1.22 ± 0.57) × 10(-11) exp[(-2100 ± 280)/T] cm(3) molecule(-1) s(-1) (uncertainties are 2σ and represent precision of the Arrhenius parameters). At 271 K ≤ T ≤ 357 K, kinetic evidence for the reversible addition reactions Br + Iso ↔ Br-Iso (k(1b), k(-1b)) and Br + Bu ↔ Br-Bu (k(3b), k(-3b)) is observed. Analysis of the approach to equilibrium data allows the temperature- and pressure-dependent rate coefficients k(1b), k(-1b), k(3b), and k(-3b) to be evaluated. At atmospheric pressure, addition of Br to each conjugated diene occurs with a near-gas-kinetic rate coefficient. Equilibrium constants for the addition/dissociation reactions are obtained from k(1b)/k(-1b) and k(3b)/k(-3b), respectively. Combining the experimental equilibrium data with electronic structure calculations allows both second- and third-law analyses of thermochemistry to be carried out. The following thermochemical parameters for the addition reactions 1b and 3b at 0 and 298 K are obtained (units are kJ mol(-1) for Δ(r)H and J mol(-1) K(-1) for Δ(r)S; uncertainties are accuracy estimates at the 95% confidence level): Δ(r)H(0)(1b) = -66.6 ± 7.1, Δ(r)H(298)(1b) = -67.5 ± 6.6, and Δ(r)S(298)(3b) = -93 ± 16; Δ(r)H(0)(3b) = -62.4 ± 9.0, Δ(r)H(298)(3b) = -64.5 ± 8.5, and Δ(r)S(298)(3b) = -94 ± 20. Examination of the effect of added O(2) on Br kinetics under conditions where reversible adduct formation is observed allows the rate coefficients for the Br-Iso + O(2) (k(2)) and Br-Bu + O(2) (k(4)) reactions to be determined. At 298 K, we find that k(2) = (3.2 ± 1.0) × 10(-13) cm(3) molecule(-1) s(-1) independent of pressure (uncertainty is 2σ, precision only; pressure range is 25-700 Torr) whereas k(4) increases from 3.2 to 4.7 × 10(-13) cm(3) molecule(-1) s(-1) as the pressure increases from 25 to 700 Torr. Our results suggest that under atmospheric conditions, Br-Iso and Br-Bu react with O(2) to produce peroxy radicals considerably more rapidly than they undergo unimolecular decomposition. Hence, the very fast addition reactions appear to control the rates of Br-initiated formation of Br-Iso-OO and Br-Bu-OO radicals under atmospheric conditions. The peroxy radicals are relatively weakly bound, so conjugated diene regeneration via unimolecular decomposition reactions, though unimportant on the time scale of the reported experiments (milliseconds), is likely to compete effectively with bimolecular reactions of peroxy radicals under relatively warm atmospheric conditio...

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Bromine Nitrate Photochemistry: Quantum Yields for O, Br, and BrO Over the Wavelength Range 248−355 nm

Cited by 14 publications

References 29 publications

Atmospheric test of the J(BrONO<sub>2</sub>)/<i>k</i><sub>BrO+NO<sub>2</sub></sub> ratio: implications for total stratospheric Br<sub>y</sub> and bromine-mediated ozone loss

Atmospheric test of the J(BrONO<sub>2</sub>)/<i>k</i><sub>BrO+NO<sub>2</sub></sub> ratio: implications for total stratospheric Br<sub>y</sub> and bromine-mediated ozone loss

The role of triplet states in the long wavelength absorption region of bromine nitrate

Kinetics of Elementary Steps in the Reactions of Atomic Bromine with Isoprene and 1,3-Butadiene under Atmospheric Conditions

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Bromine Nitrate Photochemistry: Quantum Yields for O, Br, and BrO Over the Wavelength Range 248−355 nm

Cited by 14 publications

References 29 publications

Atmospheric test of the J(BrONO&lt;sub&gt;2&lt;/sub&gt;)/&lt;i&gt;k&lt;/i&gt;&lt;sub&gt;BrO+NO&lt;sub&gt;2&lt;/sub&gt;&lt;/sub&gt; ratio: implications for total stratospheric Br&lt;sub&gt;y&lt;/sub&gt; and bromine-mediated ozone loss

Atmospheric test of the J(BrONO&lt;sub&gt;2&lt;/sub&gt;)/&lt;i&gt;k&lt;/i&gt;&lt;sub&gt;BrO+NO&lt;sub&gt;2&lt;/sub&gt;&lt;/sub&gt; ratio: implications for total stratospheric Br&lt;sub&gt;y&lt;/sub&gt; and bromine-mediated ozone loss

The role of triplet states in the long wavelength absorption region of bromine nitrate

Kinetics of Elementary Steps in the Reactions of Atomic Bromine with Isoprene and 1,3-Butadiene under Atmospheric Conditions

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Atmospheric test of the J(BrONO<sub>2</sub>)/<i>k</i><sub>BrO+NO<sub>2</sub></sub> ratio: implications for total stratospheric Br<sub>y</sub> and bromine-mediated ozone loss

Atmospheric test of the J(BrONO<sub>2</sub>)/<i>k</i><sub>BrO+NO<sub>2</sub></sub> ratio: implications for total stratospheric Br<sub>y</sub> and bromine-mediated ozone loss