| Autor: |
Long, Bo, Xia, Yu, Zhang, Yu-Qiong, Truhlar, Donald G. |
| Zdroj: |
Journal of the American Chemical Society; September 2023, Vol. 145 Issue: 36 p19866-19876, 11p |
| Abstrakt: |
Although experimental methods can be used to obtain the quantitative kinetics of atmospheric reactions, experimental data are often limited to a narrow temperature range. The reaction of SO3with water vapor is important for elucidating the formation of sulfuric acid in the atmosphere; however, the kinetics is uncertain at low temperatures. Here, we calculate rate constants for reactions of sulfur trioxide with two water molecules. We consider two mechanisms: the SO3···H2O + H2O reaction and the SO3+ (H2O)2reaction. We find that beyond-CCSD(T) contributions to the barrier heights are very large, and multidimensional tunneling, unusually large anharmonicity of high-frequency modes, and torsional anharmonicity are important for obtaining quantitative kinetics. We find that at lower temperatures, the formation of the termolecular precursor complexes, which is often neglected, is rate-limiting compared to passage through the tight transition states. Our calculations show that the SO3···H2O + H2O mechanism is more important than the SO3+ (H2O)2mechanism at 5–50 km altitudes. We find that the rate ratio between SO3···H2O + H2O and SO3+ (H2O)2is greater than 20 at altitudes between 10 and 35 km, where the concentration of SO3is very high. |
| Databáze: |
Supplemental Index |
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