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4739692 
Journal Article 
Self-Catalytic Reaction of SO3 and NH3 to Produce Sulfamic Acid and Its Implication to Atmospheric Particle Formation 
Li, H; Zhong, J; Vehkamaki, H; Kurtén, T; Wang, W; Ge, M; Zhang, S; Li, Z; Zhang, X; Francisco, JS; Zeng, XC 
2018 
Yes 
Journal of the American Chemical Society
ISSN: 0002-7863
EISSN: 1520-5126 
AMER CHEMICAL SOC 
WASHINGTON 
11020-11028 
English 
30088767 
WOS:000444219100017 
Sulfur trioxide (SO3) is one of the most active chemical species in the atmosphere, and its atmospheric fate has profound implications to air quality and human health. The dominant gas-phase loss pathway for SO3 is generally believed to be the reaction with water molecules, resulting in sulfuric acid. The latter is viewed as a critical component in the new particle formation (NPF). Herein, a new and competitive loss pathway for SO3 in the presence of abundant gas-phase ammonia (NH3) species is identified. Specifically, the reaction between SO3 and NH3, which produces sulfamic acid, can be self-catalyzed by the reactant (NH3). In dry and heavily polluted areas with relatively high concentrations of NH3, the effective rate constant for the bimolecular SO3-NH3 reaction can be sufficiently fast through this new loss pathway for SO3 to become competitive with the conventional loss pathway for SO3 with water. Furthermore, this study shows that the final product of the reaction, namely, sulfamic acid, can enhance the fastest possible rate of NPF from sulfuric acid and dimethylamine by about a factor of two. An alternative source of stabilizer for acid-base clustering in the atmosphere is suggested, and this new mechanism for NPF has implication to improved atmospheric modeling in highly polluted regions.