Kinetics of the BrO + HO₂ reaction over the temperature range T = 246–314 K

Abstract

The kinetics of the reaction between gas phase BrO and HO2 radicals, BrO + HO2 → HOBr + O2 (1), have been studied over the atmospherically relevant temperature range T = 246–314 K and at ambient pressure, p = 760 ± 20 Torr, using laser flash photolysis coupled with ultraviolet absorption spectroscopy.

Comment on “Impact of water on the BrO + HO2 gas-phase reaction: mechanism, kinetics and products” by N. T. Tsona, S. Tang and L. Du, Phys. Chem. Chem. Phys., 2019, 21, 20296

“…It is clearly important to establish the mechanism of the BrO + HO2 reaction and determine its rate coefficient at temperatures which are relevant to the troposphere (typically 220-320 K). Experimentally the rate coefficient of this reaction has been measured at different temperatures in this temperature range by a number of research groups (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) and they show that the rate coefficient decreases as the temperature increases i.e. a negative temperature dependence is observed.…”

“…They show computed schematic pathways in the work of Tsona et al(1) and Chow et al(2) respectively. The atmospheric importance of the BrO + HO2 reaction and the experimental rate coefficient (k) measurements, which show a negative temperature dependence of k, are summarized in the Suplementary Information (SI) section (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) Our work, Chow et al (2), has shown that of the possible reaction channels i.e. ( 1) BrO + HO2 → HOBr + O2, (2) BrO + HO2 → HBr + O3 , (3) BrO + HO2 → OBrO + OH, (4) BrO + HO2 → BrOO + OH, (1) has the lowest activation energies and is the major contributor to the overall rate coefficient at temperatures relevant to the troposphere.…”