A study of the reaction NO 3 + NO 2 + M → N 2 O 5 + M(M = N 2 , O 2 )

The gas‐phase reaction of the NO 3 radical with NO 2 was investigated, using a flash photolysis‐visible absorption technique, over the total pressure range 25–400 Torr of nitrogen or oxygen diluent at 298 ± 2 K. The absolute rate constants determined (in units of 10 −13 cm 3 molecule −1 s −1 ) at 25, 100, and 400 Torr total pressure were, respectively, (4.0 ± 0.5), (7.0 ± 0.7), and (10 ± 2) for M = N 2 and (4.5 ± 0.5), (8.0 ± 0.4), and (8.8 ± 2.0) for M = O 2 . These data show that the third‐body efficiencies of N 2 and O 2 are identical, within the error limits, and that previous evaluations for M = N 2 are applicable to the atmosphere. In addition, upper limits were determined for the rate constants of the reactions of the NO 3 radical with methanol, ethanol, and propan‐2‐ol of ⩽6 × 10 −16 , ⩽9 × 10 −16 , and ⩽2.3 × 10 −15 cm 3 molecule −1 s −1 , respectively, at 298 ± 2 K.