Kinetic studies of the ClO + ClO association reaction as a function of temperature and pressure

Boakes, Gavin; Mok, W. H. Hindy; Rowley, David M.

doi:10.1039/b510308h

Cited by 22 publications

(63 citation statements)

References 39 publications

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“…The Cl 2 O 2 formation rate constant k rec has been determined in a number of laboratory studies employing flash photolysis with time resolved UV absorption spectroscopy Trolier et al, 1990;Nickolaisen et al, 1994;Bloss et al, 2001;Boakes et al, 2005). Except for the most recent investigation (Boakes et al, 2005), the values given for the low pressure limit k rec,0 at temperatures above about 240 K agree well, but at stratospheric temperatures between 180 and 220 K there is a large discrepancy as shown in Fig.…”

Section: Introductionmentioning

confidence: 56%

“…The appearance of new studies has not always led to a better understanding, at least quantitatively. With the latest values reported for k rec by Boakes et al (2005) and for σ ClOOCl by Pope et al (2007) falling outside the limits of all previously published values, the uncertainties for the dimer formation and photolysis rates seem larger than ever. Some proposed parameters or combinations thereof are inconsistent in the thermodynamic properties they imply (e.g.…”

Section: Introductionmentioning

confidence: 70%

“…A large number of laboratory studies have addressed K eq (Basco and Hunt, 1979;Cox and Hayman, 1988;Nickolaisen et al, 1994;Ellermann et al, 1995;Plenge et al, 2005), k rec Trolier et al, 1990;Nickolaisen et al, 1994;Bloss et al, 2001;Boakes et al, 2005) and σ ClOOCl (Basco and Hunt, 1979;Molina and Molina, 1987;Permien et al, 1988;Cox and Hayman, 1988;DeMore and Tschuikow-Roux, 1990;Burkholder et al, 1990;Huder and DeMore, 1995;Pope et al, 2007). For each of these parameters, large discrepancies exist that often cannot be explained by the reported uncertainty limits.…”

Section: Introductionmentioning

confidence: 99%

“…For Nickolaisen et al (1994), the solid line represents the T n treatment, the dashed line the e −E/T treatment. For Boakes et al (2005) the two points at each temperature represent their results with and without incorporating an intercept in the falloff curves.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Understanding the kinetics of the ClO dimer cycle

et al. 2007

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Abstract. Among the major factors controlling ozone loss in the polar vortices in winter/spring is the kinetics of the ClO dimer catalytic cycle. Here, we propose a strategy to test and improve our understanding of these kinetics by comparing and combining information on the thermal equilibrium between ClO and Cl 2 O 2 , the rate of Cl 2 O 2 formation, and the Cl 2 O 2 photolysis rate from laboratory experiments, theoretical studies and field observations. Concordant with a number of earlier studies, we find considerable inconsistencies of some recent laboratory results with rate theory calculations and stratospheric observations of ClO and Cl 2 O 2 . The set of parameters for which we find the best overall consistency -namely the ClO/Cl 2 O 2 equilibrium constant suggested by Plenge et al. (2005), the Cl 2 O 2 recombination rate constant reported by Nickolaisen et al. (1994) and Cl 2 O 2 photolysis rates based on absorption cross sections in the range between the JPL 2006 assessment and the laboratory study by Burkholder et al. (1990) -is not congruent with the latest recommendations given by the JPL and IUPAC panels and does not represent the laboratory studies currently regarded as the most reliable experimental values. We show that the incorporation of new Pope et al. (2007) Cl 2 O 2 absorption cross sections into several models, combined with best estimates for other key parameters (based on either JPL and IUPAC evaluations or on our study), results in severe model underestimates of observed ClO and observed ozone loss rates. This finding suggests either the existence of an unknown process that drives the partitioning of ClO and Cl 2 O 2 , or else some unidentified problem with either the laboratory study or numerous measurements of atmospheric ClO. Our mechanistic understanding of the ClO/Cl 2 O 2 system is grossly lacking, with severe implications for our ability to simulate both present and future polar ozone depletion.

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Section: Introductionmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Understanding the kinetics of the ClO dimer cycle

et al. 2007

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“…JPL 2006 presents an average of Bloss et al (2001), Nickolaisen et al (1994), and Trolier et al (1990). The more recent study by Boakes et al (2005) rather increased the rate for this reaction decreasing the OClO by 6%. However, adjusting the rate constant to the lower limit of the JPL recommendations increases the OClO column by 5% at 90 • SZA and yields similar values to using Nickolaisen et al (1994) alone.…”

Section: Clo-dimer Cycle Chemistrymentioning

confidence: 99%

Evaluation of stratospheric chlorine chemistry for the Arctic spring 2005 using modelled and measured OClO column densities

et al. 2011

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Abstract. Chlorine dioxide, OClO, column amounts retrieved from measurements of the SCIAMACHY satellite instrument are presented and validated by comparison with simultaneous ground-based DOAS observations. In addition, the measurements are compared to model calculations taking into account the photochemical change along the light path.Although OClO does not participate directly in the destruction of ozone, its accurate measurement as well as modelling is crucial to understand the highly perturbed chlorine chemistry in the polar vortices. SCIAMACHY OClO slant columns retrieved during spring 2005 have been quantitatively validated by comparison with slant columns retrieved from measurements made in Ny-Ålesund (79 • N, 12 • E) and Summit (73 • N, 38 • W) as well qualitatively for Bremen (53 • N, 9 • E). Fair to good agreement is found depending on location as well as time of year.OClO slant column densities modelled with a set of stacked box models and considering the light path through the atmosphere are also included in this comparison. The model predictions differ significantly from the measured quantities. OClO amounts are underestimated for conditions of strong chlorine activation and at large solar zenith angles. Sensitivity studies for several parameters in the stacked box model have been performed and it is inferred that using the chemistry known to date, the observed OClO cannot be adequately reproduced within the range of uncertainties given for the various model parameters.

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The kinetics of the ClOOCl catalytic cycle

2016

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We use simultaneous in situ observations of [ClO] and [ClOOCl] obtained in the Arctic polar vortex to evaluate the kinetics of the ClOOCl catalytic cycle. Available laboratory measurements of the ClOOCl absorption cross sections, the ClO + ClO + M reaction rate constant, and the ClO/ClOOCl equilibrium constant are considered, along with compendium evaluations of these kinetic parameters. We show that the most recent (year 2015) recommendations for the kinetics that govern the partitioning of ClO and ClOOCl put forth by the Jet Propulsion Laboratory (JPL) panel are in extremely good agreement with the atmospheric observations of [ClO] and [ClOOCl]. Hence, we suggest that studies of polar ozone loss adopt these most recent recommendations. The most important difference with respect to calculations that rely on older recommendations is the temperature at which loss of O3 by the ClOOCl catalytic cycle terminates. The latest JPL recommendation for the equilibrium constant suggests that ClOOCl is less stable than previously assumed, resulting in an approximate 2°C downward shift in the termination temperature of polar ozone loss due to the ClOOCl catalytic cycle. Remaining uncertainties in our knowledge of the kinetics that govern the partitioning of ClO and ClOOCl within the activated vortex, and hence the efficiency of O3 loss by the ClOOCl cycle, will be best addressed by future laboratory determinations of the absolute cross section of ClOOCl at the peak (i.e., close to a wavelength of 245 nm) as well as reduced uncertainty in the rate constant of the ClO + ClO + M reaction.

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Kinetic studies of the ClO + ClO association reaction as a function of temperature and pressure

Cited by 22 publications

References 39 publications

Understanding the kinetics of the ClO dimer cycle

Understanding the kinetics of the ClO dimer cycle

Evaluation of stratospheric chlorine chemistry for the Arctic spring 2005 using modelled and measured OClO column densities

The kinetics of the ClOOCl catalytic cycle

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