Gas‐phase reaction of N 2 O 5 with water vapor: Importance of heterogeneous hydrolysis of N 2 O 5 and surface desorption of HNO 3 in a large Teflon chamber

Laboratory measurements of the gas‐phase hydrolysis of N 2 O 5 are always preturbed by wall reactions. Their contribution could be quantified in a large double‐walled teflon bag chamber by introducing HNO 3 into the chamber and analysing its temporal evolution in the gas‐phase at low and high relative humidities, and by varying the surface‐to‐volume ratio of the chamber. By fitting a model to the experimental results, a consistent set of rate coefficients for adsorption and desorption of HNO 3 from the chamber walls could be obtained. The desorption is so slow that the gas‐phase hydrolysis of N 2 O 5 via the reactions N 2 O 5 + H 2 O → 2 HNO 3 (k1 = 2.5 · 10 −22 cm ³ molec. −1 s −1 ) and N 2 O 5 + 2 H 2 O → 2 HNO 3 + H 2 O (k2 = 1.8 · 10 −39 cm 6 molec. −2 s −1 ) is influenced by wall effects to less than 5%. The importance of the gas‐phase N 2 O 5 hydrolysis in the troposphere is discussed.