Issue 17, 2011

Kinetic studies on the temperature dependence of the BrO + BrO reaction using laser flash photolysis

Abstract

The BrO self-reaction, BrO + BrO → products (1), has been studied using laser flash photolysis coupled with UV absorption spectroscopy over the temperature range T = 266.5–321.6 K, under atmospheric pressure. BrO radicals were generated via laser photolysis of Br2 in the presence of excess ozone. Both BrO and O3 were monitored via UV absorption spectroscopy using charge-coupled device (CCD) detection. Simultaneous fitting to both temporal concentration traces allowed determination of the rate constant of the two channels of reaction (1), BrO + BrO → 2Br + O2 (1a); BrO + BrO → Br2 + O2 (1b), hence the calculation of the overall rate of reaction (1) and the branching ratio, α: k1a/cm3 molecule−1 s−1 = (1.92 ± 1.54) × 10−12 exp[(126 ± 214)/T], k1b/cm3 molecule−1 s−1 = (3.4 ± 0.8) × 10−13 exp[(181 ± 70)/T], k1/cm3 molecule−1 s−1 = (2.3 ± 1.5) × 10−12 exp(134 ± 185 /T) and α = k1a/k1 = (0.84 ± 0.09) exp[(−7 ± 32)/T]. Errors are 1σ, statistical only. Results from this work show a weaker temperature dependence of the branching ratio for channel (1a) than that found in previous work, leading to values of α at temperatures typical of the Polar Boundary Layer higher than those reported by previous studies. This implies a shift of the partitioning between the two channels of the BrO self-reaction towards the bromine atom and hence directly ozone-depleting channel (1a).

Graphical abstract: Kinetic studies on the temperature dependence of the BrO + BrO reaction using laser flash photolysis

Article information

Article type
Paper
Submitted
10 Dec 2010
Accepted
04 Mar 2011
First published
25 Mar 2011

Phys. Chem. Chem. Phys., 2011,13, 7997-8007

Kinetic studies on the temperature dependence of the BrO + BrO reaction using laser flash photolysis

V. Ferracci, K. Hino and D. M. Rowley, Phys. Chem. Chem. Phys., 2011, 13, 7997 DOI: 10.1039/C0CP02847A

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