UV-visible absorption cross sections of bromine nitrate determined by photolysis of BrONO2/Br2 mixtures

Abstract

Experiments on the determination of absorption cross sections of bromine nitrate by photolysis of BrONO2/Br2 mixtures were carried out using a UV-visible absorption spectrometer. The relatively stable end products of photolysis were identified as Br2 and N2O5. NO3 was observed as intemedaite product in the photolysis of BrONO2/Br2. Absorption cross sections for BrONO2 at 298 K and 230 K were determined between 208 and 500 nm. The results are in good agreement with a recent independent study. Calculations of atmospheric photolysis rates of BrONO2 as a function of solar zenith angle and surface albedo were undertken using the PHOTOGT program. The latter are in the range between0.5×10-3s-1 and 4.0×10-3s-1., indicating that during daylight BrONO2 is rapidly photolyzed.