STRUCTURE AND STABILITY OF [H-2,O-2](- AN AB-INITIO MOLECULAR-ORBITALSTUDY() DOUBLET AND QUARTET STATE CATIONS )

High-level ab initio calculations in the framework of the G2 theory ha ve been performed for the [H-2, O-2](+) doublet and quarter state cati ons. The geometries of the different minima of both potential energy s urfaces were optimized at the QCISD/6-31+G(df,p) level. The bonding ch aracteristics of doublet and quarter state cations are rather differen t. The latter are weakly bound species involving one-electron linkages , while the former present normal covalent bonds. The global minimum o f the doublet PES is the HO-OH+ 2Dt species, which has an O-O linkage with a partial double-bond character. This means that the ionization o f hydrogen peroxide implies an important enhancement of the stability of the peroxidic bond, which upon ionization becomes much shorter, whi le its stretching frequency is significantly blue-shifted. For the qua rters the global minimum is the O-OH2+ oxywater cation, which can be v iewed roughly as the interaction between O+ in its S-4 ground state an d water. Such interaction implies the formation of a one-electron O-O bend. As a consequence of the relatively low stabilities of the quarte r cations, the global minimum of both PESs is the HO-OH+ 2Dt doubler s tate species.