Exploring the chemical fate of the sulfate radical anion by reaction with sulfur dioxide in the gas phase

• Main Authors: N. T. Tsona, N. Bork, H. Vehkamäki
• Format: Article
• Language: English
• Published: Copernicus Publications 2015-01-01
• Series: Atmospheric Chemistry and Physics
• Online Access: http://www.atmos-chem-phys.net/15/495/2015/acp-15-495-2015.pdf
• ISSN: 1680-7316; 1680-7324

The gas phase reaction between SO₄^&minus;(H₂O)_<i>n</i> and SO₂, <i>n</i> = 0–2, is investigated using ab initio calculations and kinetic modelling. Structures of reactants, transition states and products are reported. Our calculations predict that the SO₂SO</sub>₄^&minus;(H₂O)_<i>n</i> cluster ion, which is formed upon SO₂ and SO₄^&minus;(H₂O)_<i>n</i> collision, can isomerize to SO₃SO₃^&minus;(H₂O)_<i>n</i>. The overall reaction is SO₂ oxidation by the SO₄^&minus;(H₂O)_<i>n</i> anionic cluster. The results show that SO₄^&minus;(H₂O)_<i>n</i> is a good SO₂ oxidant, especially at low relative humidity, with a reaction rate constant up to 1.5 &times; 10^&minus;10 cm³ molecule^&minus;1s^&minus;1. At high relative humidity, instead, the re-evaporation of SO₂ from the SO₂SO</sub₄^&minus;(H₂O)_<i>n</i> cluster ion is favoured.