Eli was looking for something science like to write about when he came across the above titled paper by Neil Donahue. Now some, not Eli to be sure, could resist.
The transformation of SO2 to SO3 and thence by reaction with water (H2O) to sulfuric acid (H2SO4) is the key step in forming sulfate aerosols, which, in turn can reflect and absorb considerable sunlight, or act as cloud condensation nuclei again, increasing the Earth's albedo. Serious (well this is Rabett Run) consideration has been given to the idea of counteracting greenhouse gas warming by injecting SO2 into the atmosphere, although this would accelerate acidification of lakes and oceans.
For some time atmospheric chemists have waved their hands over the oxidation process
but there is not enough HO in the atmosphere to match the observed sum of SO3 and H2SO4.
Another mystery has long been the existence of the Crigee Intermediate (aka CI). Over 50 years ago Rudolph Crigee proposed that ozonolysis (react ion with ozone where a carbon carbon double bond is replaced by a double bond between a carbon and an oxygen atom) of alkenes (stuff with a double bond between two carbon atoms) initially formed a biradical (a molecule with two unpaired electrons). Everyone accepts the mechanism, there is a huge amount of work consistent with its existence, see the Donahue paper above, but it had never been directly observed and rate constants were guessed at, but not measured, or at best inferred
As they pointed out, this meant that NO3 and SO3 would be produced efficiently by reactions with the CI and the effects on atmospheric chemistry would be significant where there were enough alkene precursors. How significant, well as significant as the oxidation of SO2 by OH, and for NO3 it would account for up to a 20% increase.