Rate constant of the BrO + BrO reaction over the temperature range 220‐950 K

Abstract

AbstractThe kinetics of the self‐reaction of BrO radicals has been studied over a wide temperature range (T = 220‐950 K) at 2 Torr total pressure of He using a low‐pressure flow reactor combined with a quadrupole mass spectrometer: BrO + BrO → 2Br + O2 (1a) and BrO + BrO → Br2 + O2 (1b). The overall rate constant for this reaction (defined by d[BrO]/dt = –2k1[BrO]2) was found to be k1 = k1a +k1b = (1.32 ± 0.09) × 10−12 exp(182 ± 22/T) cm3 molecule−1 s−1 at T = 220‐950 K (where the uncertainties represent precision at the 2σ level). The channel‐specific rate constant for the Br2 + O2 forming channel (1b) was determined at T = 220‐450 K: k1b = (2.83 ± 0.35) × 10−13 exp(34 ± 36/T) cm3 molecule−1 s−1 (with 2σ uncertainties). As a result of the comparative analysis of the present data and those from the previous studies, the following Arrhenius expressions are recommended from the present work: k1 = 1.4 × 10−12 exp(200/T) at T = 220‐950 K (independent of pressure at least for T ≥ 250 K) and k1b = 3.2 × 10−13 exp(34/T) cm3 molecule−1 s−1 at T = 220‐450 K and total pressure of 2 Torr, with a conservative estimate of uncertainty of 25%, independent of temperature.