Photodissociation of BrONO2 and N2O5: Quantum Yields for NO3 Production at 248, 308, and 352.5 nm

Quantum yields for NO 3 production in the photolysis of BrONO 2 and N 2 O 5 were measured at 248, 308, and 352.5 nm. The measured values for BrONO 2 were found to be independent of pressure over the range 150−600 Torr and bath gas (N 2 or O 2 ) and are 0.28 ± 0.09, 1.01 ± 0.35, and 0.92 ± 0.43 at 248, 308, and 352.5 nm, respectively. Quantum yields of Br and BrO in the photolysis of BrONO 2 were also estimated. The measured values for NO 3 production in the photolysis of N 2 O 5 were 0.64 ± 0.10, 0.96 ± 0.15, and 1.03 ± 0.15 at 248, 308, and 352.5 nm, respectively. Rate coefficients for the reactions Br + BrONO 2 → Br 2 + NO 3 (18) and Cl + BrONO 2 → ClBr + NO 3 (19) were measured at 298 K to be k 18 = (6.7 ± 0.7) × 10 -11 cm 3 molecule -1 s -1 and k 19 = (1.27 ± 0.16) × 10 -10 cm 3 molecule -1 s -1 . The NO 3 product yields for reactions 18 and 19 were measured to be 0.88 ± 0.08 and 1.04 ± 0.24, respectively. The absorption cross sections for N 2 O 5 between 208 and 398 nm are also reported. All quoted uncertainties are 2σ and include estimated systematic errors. On the basis of the measured quantum yields of NO 3, the atmospheric photolysis rate of BrONO 2 is discussed.