Metastable State of the Doubly Charged Carbon Dioxide Ion

A metastable state in CO2++ dissociating into CO++O+ with a half-life of 2.3±0.2 μsec has been observed. The corresponding metastable peaks are observed at (M1/q1)*=35.6 and (M2/q2)*=11.6, respectively. The widening of these peaks with accelerating voltage shows the repulsion energy to be 2.7 eV and the corresponding charge separation at fragmentation to be 5.3 Å. The appearance potential of CO2++ was found to be 38.0±0.2 eV, and this value is discussed in terms of the various repulsion energies and energy balances. The data is consistent with the hypothesis of an immediate fragmentation into CO+(2Σ) and O+ and the metastable fragmentation into CO+(2IIi) and O+. The fragmentation of CO2++ enriched in O18 has also been reinvestigated. It is shown that the unsymmetrical doubly charged molecule ion (CO16O18++) has a lower yield than the corresponding symmetrical molecule ions containing O16 and O18, respectively.