Roaming Pathway in Ionized CO2

Determine whether an intramolecular roaming mechanism operates in ionized carbon dioxide (CO2), as an alternative to the transition-state bond rearrangement mechanism for central carbon elimination and O–O bond formation, given that the existence of a roaming pathway in ionized CO2 was previously unknown both experimentally and theoretically.

Background

The paper reviews two mechanisms for producing molecular oxygen from excited CO2: a transition-state pathway involving bending deformation and O–O bond formation, and a roaming pathway in which one C–O bond breaks and a quasifree O atom wanders before intramolecular abstraction to form a C–O–O isomer. Prior work on ionized CO2 had proposed only the transition-state pathway, leaving the possibility of roaming unverified.

The authors note explicitly that, for ionized CO2, the roaming pathway was unknown both experimentally and theoretically. This unknown motivates their combined experimental and theoretical investigation into O2+ formation from CO2 dications and the identification of a roaming mechanism. The quoted sentence captures the explicit uncertainty that existed before their paper.