An electron transfer mechanism of O4 formation

A resonating valence bond electron transfer mechanism of combining two O2 molecules to form an O4 molecule is presented. The predicted molecular states of the reaction path D∞h→C2v→D2h are supported by the present ab initio molecular orbital calculations. The CASPT2 BSSE calculations yield a stable diamagnetic D2h O4 molecule with a very weak chemical bond between the monomers, in good agreement with experiments. A low activation barrier energy of ∼26 cal/mol for the O4 formation is found.