An ab initio study on the mechanism of the F + O3 → FO + O2 reaction: comparative reactivity study along the isoelectronic NH2, OH and F radicals series

The title reaction has been theoretically studied by using MP2, QCISD, QCISD(T), CCSD(T), CASSCF, and CASPT2 methods with various basis sets. At single-reference MP2 and QCISD levels of theory, the potential energy hypersurface (HPES) shows a two-step reaction mechanism through two transition states (TS1 and TS2) and an intermediate (Int). However, the multiconfigurational CASSCF HPES shows a one-step reaction mechanism, as was previously found for the NH2 + O3 and OH + O3 reactions. The results show that the reactivity of the isoelectronic series of NH2, OH, and F radicals increases from the amino radical to the fluorine atom.