AN UPPER LIMIT ON THE PRODUCTION OF N2O FROM THE REACTION OF O(D-1) WITH CO2 IN THE PRESENCE OF N-2

While the major sources and sinks of N2O are known, there is debate co ncerning additional processes. A new source of N2O was proposed, react ion of N-2 With excited CO3, formed from O(D-1) and CO2. Mixtures of O-3, CO2, N-2, and O-2 at total pressures of 1 atm were photolyzed at 254 nm to form O(D-1). The decrease in O-3 and a search for N2O format ion were carried out using FTIR at 298 K and similar to 264 K. N2O was not detected at either temperature. Upper limits were derived for the rate constant of the reaction CO3 + N-2 --> N2O + CO2, k less than o r equal to 5.5x10(-13)) cm(3) molecule(-1) s(-1) at 298 K and k less t han or equal to 4.2x10(-13) cm(3) molecule(-1) s(-1) at 264 K. Applyin g the rate constant at 264 K to typical stratospheric conditions at th e spring: equinox, 17 km and 40 degrees N, the N2O formation rate was calculated to be II molecule cm(-3) s(-1). These experiments did not u se isotopically heavy reactants and therefore may underestimate the N2 O yield. It is assumed that the results of these studies are applicabl e to stratospheric conditions. It is also assumed that N2O is not dest royed as it is formed by unrecognized secondary reactions. However, wi thin these constraints, the upper limit suggests that this reaction is not a significant source of N2O.