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

TL;DR

This study investigates the lifetimes of carbon monoxide dications produced by ion collisions, revealing metastable states with varying durations and contrasting fragmentation mechanisms, thereby advancing understanding of molecular ion stability.

Contribution

It provides experimental evidence of metastable CO$^{2+}$ states with lifetimes from 2 ps to 200 ns using dimer fragmentation analysis.

Findings

Metastable states with diverse lifetimes are observed.

Fast dissociation channels are identified and characterized.

Contradicts previous assumptions about neighbor molecule effects.

Abstract

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.