Rate constant of the gas phase reaction of SO3 with H2O

Abstract
The rate constants for the reaction of SO3 with H2O in He and in N2 were measured at total pressures from 1–10 Torr in a flow tube at room temperature. The concentration of SO3 was monitored by photofragment emission produced by 147 nm excitation. Dependencies of apparent reaction rates on wall conditions and reaction tube sizes were investigated. At total He pressures of 1–10 Torr, a value of (5.7±0.9)×10−15 cm3 /s was obtained for the upper limit of the homogeneous gas phase reaction rate constant. This rate value is more than two orders of magnitude lower than the previously published value, but it is consistent with the theoretical calculation provided in this paper.