13444-87-6Relevant articles and documents
Temperature-dependent rate coefficients for the reactions of Br(2P3/2), Cl(2P3/2), and O(3PJ) with BrONO2
Soller,Nicovich,Wine
, p. 1416 - 1422 (2007/10/03)
A laser flash photolysis-resonance fluorescence technique has been employed to investigate the kinetics of reactions of the important stratospheric species bromine nitrate (BrONO2) with ground-state atomic bromine (k1), chlorine (k2), and oxygen (k3) as a function of temperature (224-352 K) and pressure (16-250 Torr of N2). The rate coefficients for all three reactions are found to be independent of pressure and to increase with decreasing temperature. The following Arrhenius expressions adequately describe the observed temperature dependencies (units are 10-11 cm3molecule-1s-1): k1 = 1.78 exp(365/T), k2 = 6.28 exp(215/T), and k3 = 1.91 exp(215/T). The accuracy of reported rate coefficients is estimated to be 15-25% depending on the magnitude of the rate coefficient and on the temperature. Reaction with atomic oxygen is an important stratospheric loss process for bromine nitrate at altitudes above approximately 25 km; this reaction should be included in models of stratospheric chemistry if bromine partitioning is to be correctly simulated in the 25-35 km altitude regime.
Kinetics of the gas-phase reaction of BrNO2 with NO
Bro?ske,Zabel
, p. 8626 - 8631 (2007/10/03)
BrNO2 was prepared in situ in a static reactor (v = 420 L) by photolyzing Br2/NO2/N2 mixtures in the wavelength range 500-700 nm at temperatures between 263 and 294 K. After the lights were switched off, the excess NO was added, and IR and UV spectra were monitored simultaneously as a function of time. From the pseudo-first-order decay of the IR absorption of BrNO2 in the presence of a large excess of NO, the second-order rate constant for reaction 4, BrNO2 + NO → BrNO + NO2, was determined to be k4 = 2.3 × 10-12 exp[(-17.8 ± 2.1) kJ mol-1/RT] cm3molecule-1s-1 (2σ). The measured yields of BrNO were close to 100percent (98 ± 5percent). These results suggest that reaction 4 is unimportant as a loss process of BrNO2 under most tropospheric conditions. Additional experiments on the thermal stability of BrNO2 led to an upper limit of 4.0 × 10-4 s-1 for its thermal gas-phase decomposition rate constant at 298 K in 1 atm of synthetic air. Finally, the mechanism of the Br + NO2 reaction and the thermochemistry of BrNO2 and BrONO are discussed in light of the results of the present experiments and of previous work from the literature.