Electron capture induced fragmentation of CO3+2: Influence of projectile charge on sequential and concerted break-up pathways

Abstract

We investigate the O+: C+: O+ fragmentation channel of CO3+2 produced in slow collisions with Ar𝑞+ projectiles (4≤𝑞≤16, velocities ≈0.3 a.u). Using the native-frames method, we disentangle the sequential and concerted break-up processes and their corresponding kinetic energy release (KER) distributions. Ab initio potential energy curves of CO3+2 are calculated and mapped to the KER spectra to identify the underlying electronic states involved in the fragmentation. While the sequential KER distributions remain nearly unchanged for across the projectile charge range, the concerted KER distributions exhibit pronounced but non-systematic variations with projectile charge. For low charge projectiles an additional feature at ≈15.5eV is seen in the concerted KER distribution, which, in past works, has been attributed to sequential processes. The branching ratio shifts in favor of sequential break-up as 𝑞 increases, consistent with expectations from classical descriptions of electron capture. Departures from a monotonic increase with 𝑞 are observed for specific projectiles, indicating that, in addition to the projectile charge, its electronic structure must also be taken into account to understand capture induced fragmentation.