Identification and theoretical investigation of the SiO2+ dication

The gas-phase diatomic dication SiO2+ has been observed by mass spectrometry and identified by its isotopic abundance. It was produced by energetic, high-current oxygen (16O−) ion beam sputtering of a silicon surface and survived a flight time of ∼10−5 s. In addition, a detailed theoretical study of SiO2+ has been performed. Our calculations show that SiO2+ is a metastable species with a large potential barrier towards dissociation (∼1.55 eV for the SiO2+ X ground state). We have derived a set of accurate spectroscopic constants and transition energies for SiO2+. The adiabatic double ionization energy of SiO is ∼31 eV.