A SPECTROSCOPIC STUDY OF THE EQUILIBRIUM NO2+NO3+M-REVERSIBLE-N2O5+M AND THE KINETICS OF THE O3/N2O5/NO3/NO2/AIR SYSTEM

The equilibrium constant, K(eq) of the reaction NO2 + NO3 + M irreversible N2O5 + M has been determined for a small range of temperatures around room temperature in air at 740 torr by direct spectroscopical measurements of NO2, NO3, and N2O5. At 298 K, K(eq) was determined as (3.73 +/- 0.61) x 10(-11) cm3 molecule-1. Averaging this and 11 other independent evaluations of K(eq) yields K(eq) = (3.31 +/- 0.82) x 10(-11) cm3 molecule-1, where the uncertainty is given as one standard deviation. The kinetics of the O3/NO2/N2O5/NO3/air system was studied in a static chamber at room temperature and 740 torr total pressure. Evidence of a unimolecular decay reaction of NO3, NO3 --> NO + O2, was found and its rate coefficient was estimated as (1.6 +/- 0.7) x 10(-3) s-1 at 295 +/- 2 K.