Branching ratios for the O( 1 D ) + N 2 O reaction

Laboratory studies of the branching ratio of the reaction of electronically excited oxygen atoms, O( 1 D ), with nitrous oxide, N 2 O, were performed by measuring the loss of N 2 O and the formation of products in a static optical cell interfaced to a Fourier transform spectrometer system. The results agree well with the most recent measurements, and a critical evaluation of the available data results in a factor of 2 reduction in the uncertainty. The ratio k 1 b / k 1 is the fraction of reaction leading to the production of NO (reaction (1 b )) relative to the total reaction of O( 1 D ) with N 2 O (reaction (1)). The present recommendation for this ratio as it pertains to atmospheric reactions is 0.61±0.08 (95% confidence interval). The consequences of this result in terms of stratospheric NO y production and field measurements of ozone photolysis rates are discussed.