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J. Phys. Chem. A 1997, 101, 10000-10011
Pressure and Temperature Dependence of the Gas-Phase Reaction of SO3 with H2O and the Heterogeneous Reaction of SO3 with H2O/H2SO4 Surfaces John T. Jayne,† Ulrich Po1 schl,‡ Yu-min Chen,‡ David Dai,‡ Luisa T. Molina,‡ Douglas R. Worsnop,† Charles E. Kolb,† and Mario J. Molina*,‡ Center for Chemical and EnVironmental Physics, Aerodyne Research, Inc., Billerica, Massachusetts 01821-3976, and Department of Chemistry and Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 ReceiVed: August 4, 1997; In Final Form: October 10, 1997X
The gas-phase reaction of SO3 with H2O and the heterogeneous reaction of SO3 with H2O-H2SO4 surfaces have been studied in a fast flow reactor coupled to a chemical ionization mass spectrometer (CIMS) for species detection. The gas-phase reaction was studied under turbulent flow conditions over the pressure range from 100 to 760 Torr N2 and the temperature range from 283 to 370 K. The loss rate of SO3 was measured under pseudo-first-order conditions; it exhibits a second-order dependence on water vapor concentration and has a strong negative temperature dependence. The first-order rate coefficient for the SO3 loss by gas-phase reaction shows no significant pressure dependence and can be expressed as kI(s-1) ) 3.90 × 10-41 exp(6830.6/T)[H2O]2 where [H2O] is in units of molecule cm-3 and T is in Kelvin. The overall uncertainty of our experimentally determined rate coefficients is estimated to be (20%. At sufficiently low SO3 concentrations (
