Third‐order rate constants of atmospheric importance

Patrick, Roger; Golden, David M.

doi:10.1002/kin.550151107

Cited by 99 publications

(108 citation statements)

References 26 publications

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“…As long as the choice of r H • (0 K) is consistent, the e − r H • (0 K)/RT and e −E 0 /RT terms in Eqs. (3) and (4) cancel and the remaining dependency on E 0 (mainly through ρ vib,h ) and hence on the choice of the equilibrium constant is small (Patrick and Golden, 1983). The following expression is obtained:…”

Section: Introductionmentioning

confidence: 99%

“…As pointed out by Patrick and Golden (1983) and stressed in Crowley (2006) and Golden (2006), rate theory is far from being perfect and Eq. (4) involves a number of approximations.…”

Section: Introductionmentioning

confidence: 99%

“…2. We compare the low pressure limiting rate constants k diss,0 from these studies to theoretical calculations using unimolecular rate theory described by the following formalism (Troe, 1977a;Troe, 1977b;Troe, 1979; (2001) 1.99×10 −30 ×T 8854 von Hobe et al (2005) 3.61×10 −27 8167 Plenge et al (2005) 1.92×10 −27 8430±326 a Factor of 1.2 uncertainty at 298 K and factor of 2 uncertainty at 200 K. Patrick and Golden, 1983):…”

Section: Introductionmentioning

confidence: 99%

“…Z LJ is the Lennard-Jones collision frequency, ρ vib,h (E 0 ) the harmonic oscillator density of states, Q vib the vibrational partition function, E 0 ∼ = r H • (0 K) the reaction threshold energy (note that in Table 2, r H • values are given for the forward direction of Reaction (R1), so the sign has to be reversed here), F anh the anharmonicity correction, F E the energy dependence of the density of states and F rot the external rotational contribution. The correction factor for internal rotation, F rot int , is not considered here because internal rotors are not significant at low temperatures for these calculations (Patrick and Golden, 1983). Following Troe (1977b) we neglect the final factor F corr introduced to correct for the coupling between the various factors and the approximations made in the calculation.…”

Section: Introductionmentioning

confidence: 99%

“…Effective rate constants are estimated using the following expression (Troe, 1979;Patrick and Golden, 1983):…”

Section: Introductionmentioning

confidence: 99%

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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: 99%

“…As pointed out by Patrick and Golden (1983) and stressed in Crowley (2006) and Golden (2006), rate theory is far from being perfect and Eq. (4) involves a number of approximations.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Effective rate constants are estimated using the following expression (Troe, 1979;Patrick and Golden, 1983):…”

Section: Introductionmentioning

confidence: 99%

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Understanding the kinetics of the ClO dimer cycle

et al. 2007

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Impact of SO2 and NO on CO oxidation under post-flame conditions

Glarborg

Kubel

Dam‐Johansen

et al. 1996

Int. J. Chem. Kinet.

141

128

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An experimental and theoretical study on the effect of SO2 on moist CO oxidation with and without NO present has been carried out. The experiments were performed in an isothermal quartz flow reactor at atmospheric pressure in the temperature range 800–1300 K. Inlet concentrations of SO2 ranged from 0 to 1800 ppmv, while the NO ranged between 0, 100, or 1500 ppm. SO2 inhibits CO oxidation under the conditions investigated, shifting the fast oxidation regime 20–40 K towards higher temperatures at 1500 ppm SO2. The inhibition is most pronounced at high O atom levels. The experimental data supported by model analysis suggest that SO2 primarily reacts with O atoms forming SO3, which is subsequently consumed mainly by reaction with O and HO2. Addition of NO significantly diminishes the effect of SO2. Since NO is usually present in combustion flue gases, the impact of SO2 on CO burnout in most practical systems is projected to be small. The H/S/O thermochemistry and reaction subset has been revised based on recent experimental and theoretical results, and a chemical kinetic model has been established. The model provides a reasonable overall description of the effect of SO2 and NO on moist CO oxidation, while the SO3/SO2 ratio is well predicted over the range of conditions investigated. In order to enhance model performance further, rate constants for a number of SO2 and SO3 reactions need to be determined with higher accuracy. © 1996 John Wiley & Sons, Inc.

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Chlorine Perchlorate Formation in the Gas Phase Photolysis of Chlorine Dioxide

Zabel

1991

Ber Bunsenges Phys Chem

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Chemical Kinetics J Elementary Reactions / Photochemistry / Radicals OC10/02/N2 mixtures were photolyzed in a temperature controlled 420 1 reaction chamber at temperatures between 249 and 300 K and total pressures between 0.5 and lo00 mbar. Initial OClO concentrations were in the range (1.7-5.7) . lo'' rnolecule/cm'. Reaction mixtures were analyzed in situ via long-path IR absorption using a Fourier-transform spectrometer. In some experiments product spectra were simultaneously monitored in the IR and the UV. Depending on reaction conditions, the product IR spectra were dominated by absorption bands of C1203 or c 1 2 0 4 or a mixture of both. Evidence is presented for the crucial role of 0 atoms in the C1204 formation, suggesting either of the two mechanisms:Both the weak temperature dependence and the strong pressure dependence of the CI2O4 yield support mechanism (I). In addition, CI2O6 was detected as a minor product of OClO photolysis under certain reaction conditions, both by its IR and UV absorption. ResultsDuring OClO photolysis at 249 K, five strong IR absorption bands developed with time originating from at least two different Ber. Bunsenges. Phys. Chem. 95 (1991) No. 8 0 VCH Verlagsgesellschaft mbH, W-6940 Weinheim. 1991 0005-9021/ 91~0808-0893 d 3.50+ ,2510 The rate constant kq of quenching of singlet oxygen (lo2) by 1,4-diazobicyclo[2.2.2]octane (DABCO) has been determined in six solvents in dependence of pressure using time resolved phosphorescence techniques. Experimental activation volumes vary between -19.0 ml.mol-' (chloroform) 5 AV& -10.0 ml . mol-' (benzonitrile). The data are analyzed by means of a kinetic scheme assuming a preequilibrium of '02 and DABCO to form a singlet contact complex IC. The data are consistent with the assumption that the deactivation of '02 occurs via a charge transfer process between the collision partners of C converting 'C to 'C, which subsequently splits into the deactivation products. The statistical model developed by Yoshimura and Nakahara is used to calculate the reaction volume AV, of the preequilibrium. AV, and the activation volume AV& of the actual deactivation of '02 by DABCO contribute practically in equal parts to AV&. AV& values strongly depend on the solvent polarity. On the basis of Kirkwood's electrostriction model the actual activation volume (AV&)O without electrostriction effect and the dipole moment of the transition state , I & have been estimated to: ( A ? ' & ) ' = -4.3 ml.mol-' and p& = 7.8 Debye, respectively.

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Third‐order rate constants of atmospheric importance

Cited by 99 publications

References 26 publications

Understanding the kinetics of the ClO dimer cycle

Understanding the kinetics of the ClO dimer cycle

Impact of SO2 and NO on CO oxidation under post-flame conditions

Chlorine Perchlorate Formation in the Gas Phase Photolysis of Chlorine Dioxide

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