We have performed a detailed theoretical study applying large ab initio computations of the low lying electronic states of ClO(2+) and ClO(3+) and an experimental search for these ClO(2+) and ClO(3+) gas-phase species. For both species, we have found electronic states with potential barriers with respect to dissociation, where these multiply positively charged diatomic ions can exist in the gas phase as long-lived metastable molecules. Our potential energy curves are used to predict the double-ionization spectrum of ClO and to derive a set of spectroscopic parameters for the metastable bound states of these species. At the MRCI + Q/aug-cc-pV5Z level, the adiabatic double and triple ionization energies of ClO are computed to be 32.4 eV and 65.0 eV, respectively. Experimentally, we confirm the existence of ClO(2+) using mass spectrometry. ClO(2+) could be produced by energetic, high-current oxygen ((16)O(-)) ion beam sputtering of PdCl(2) and NH(4)Cl powders and survived a flight time of ~9 μs. We report also the experimental observation of the ClN(2+), PdCl(2+) and InO(2+) diatomic doubly charged ions.
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