Methanesulfonic acid (MSA) and SO3 formation from the addition channel of atmospheric dimethyl sulfide oxidation†

The formation of methanesulfonic acid (MSA) from the dimethyl sulfide addition channel primarily proceeds via the reaction of methylsulfonyloxy radicals (CH₃SO₃) with H-atom donors, other than HO₂ radicals. In competition with it, thermal decomposition of CH₃SO₃ results in SO₃ generation. The MSA/SO₃ ratio is driven by the temperature dependence of CH₃SO₃ decomposition.