Pressure and temperature dependence kinetics study of the NO + BrO → NO_2 + Br reaction. Implications for stratospheric bromine photochemistry

The flash photolysis-ultraviolet absorption technique has been utilized to study the reactivity of nitric oxide with BrO radicals over a wide range of pressure (100-700 torr) and temperature (224-398 K). Pseudo-first-order conditions were used in order to minimize complications caused by secondary kinetic processes. The reaction and its corresponding Arrhenius expression in units of cm^3 molecule^(-1) s^(-1) can be written NO + BrO → NO_2 + Br ΔHº_298 = -17.0 kcal mol^(-1) k_1 = (1.28 ± 0.23) x 10^(-11)exp((181 ± 46)/T) (T = 224-398 K) The results are compared with previous measurements, and atmospheric implications of the reaction are discussed. It is shown that this reaction is important in controlling the ratios [BrO]/[Br] and [BrO]/[HBr] in the stratosphere but that it does not affect the catalytic efficiency of BrO, in ozone destruction