Revealing new pathways for the reaction of Criegee intermediate CHOO with SO.

Criegee intermediates play an important role in the tropospheric oxidation models through their reactions with atmospheric trace chemicals. We develop a global full-dimensional potential energy surface for the CHOO + SO system and reveal how the reaction happens step by step by quasi-classical trajectory simulations. A new pathway forming the main products (CHO + SO) and a new product channel (CO + H + SO) are predicted in our simulations. The new pathway appears at collision energies greater than 10 kcal/mol whose behavior demonstrates a typical barrier-controlled reaction. This threshold is also consistent with the ab initio transition state barrier height. For the minor products, a loose complex OCHO ∙ ∙ ∙ SO is formed first, and then in most cases it soon turns into HCOOH + SO, in a few cases it decomposes into CO + H + SO which is a new product channel, and rarely it remains as ∙OCHO ∙ + SO.