UV VISIBLE AND IR ABSORPTION CROSS-SECTIONS OF BRONO2

The absorption cross sections of BrONO2 between 200 and 500 nm were measured over the temperature range 298 to 220 K using a diode array spectrometer. The BrONO2 absorption cross sections are weakly dependent on temperature at wavelengths < 450 nm (less than 10% change between 298 and 220 K) but decrease rapidly with decreasing temperature at wavelengths > 450 nm; at 480 nm the cross section decreased by similar to 35% in going from 298 K to 220 K. Our room temperature absorption cross sections are in good agreement with the measurements of Spencer and Rowland (1978) over the common wavelength range of the measurements, 200 to 390 nm. We show that wavelengths longer than 390 nm must be included in the calculation of the BrONO2 atmospheric photolysis rate. We also show that photolysis of BrONO2 could be a significant atmospheric loss process for odd oxygen (due to halogen chemistry) below about 25 km, The infrared absorption cross sections for the BrONO2 band centered at 803.3 cm(-1) were also measured. The integrated band strength was (2.7 +/- 0.5) x 10(-17) cm(2) molecule(-1) cm(-1).