The reaction probability of N₂O₅ with sulfuric acid aerosols at stratospheric temperatures and compositions

Abstract

We have measured the rate of reaction of N 2 O 5 with H 2 O on monodisperse, submicrometer H 2 SO 4 particles in a low‐temperature flow reactor. Measurements were carried out at temperatures between 225 K and 293 K on aerosol particles with sizes and compositions comparable to those found in the stratosphere. At 273 K, the reaction probability was found to be 0.103±0.006, independent of H 2 SO 4 composition from 64 to 81 wt %. At 230 K, the reaction probability increased from 0.077 for compositions near 60% H 2 S0 4 to 0.146 for compositions near 70% H 2 SO 4 . Intermediate conditions gave intermediate results except for low reaction probabilities of about 0.045 at 260 K on aerosols with about 78% H 2 SO 4 . The reaction probability did not depend on particle size. These results imply that the reaction occurs essentially at the surface of the particle. A simple model for this type of reaction that reproduces the general trends observed is presented. The presence of formaldehyde did not affect the reaction rate.