Ab initio study on the paths of oxygen abstraction of hydrogen trioxide (HO3) molecule in the HO3 + SO2 reaction

The reaction paths of hydrogen trioxide (HO3) with sulphur dioxide (SO2) have been investigated on the doublet potential energy surface, theoretically. All species of the title reaction have been optimized at the PMP2(FC)/cc-pVDZ computational level. Energetic data have been obtained at the CCSD(T)//PMP2 level employing the cc-pVDZ basis set. No stable collision complexes have been found between the SO2 and HO3 molecules. Therefore, the SO2 + HO3 reaction starts without initial associations. The four possible paths, P1 through P4, have been obtained for the formation of SO3 (D 3h) + HOOâ̂™ product. Our results show that these four paths include relatively high energy barriers to produce the final product of the SO3 (D 3h) + HOOâ̂™. Therefore, the SO2 + HO3 → SO3(D 3h) + HOOâ̂™ reaction is difficult to perform under atmospheric conditions. This means that the importance of SO2 + HO3 → SO3 (D 3h) + HOOâ̂™ reaction increases with increasing temperature and, this reaction plays an important role in the SO3(D 3h) production as the main molecule of the formation of acid rain at high temperatures. [Figure not available: see fulltext.] © 2013 Indian Academy of Sciences.