Investigation of the Carbon Monoxide Dication Lifetime Using (CO)$_2$ Dimer Fragmentation

The fragmentation of carbon monoxide dimers induced by collisions with low energy Ar$^{9+}$ ions is investigated using the COLTRIMS technique. The presence of a neighbor molecule in the dimer serves here as a diagnostic tool to probe the lifetimes of the $\rm CO^{2+}$ molecular dications resulting from the collision. The existence of metastable states with lifetimes ranging from 2~ps to 200~ns is clearly evidenced experimentally through a sequential 3-body fragmentation of the dimer, whereas fast dissociation channels are observed in a so-called concerted 3-body fragmentation process. The fast fragmentation process leads to a kinetic energy release distribution also observed in collisions with monomer CO targets. This is found in contradiction with the conclusions of a former study attributing this fast process to the perturbation induced by the neighbor molecular ion.