Contribution of different electron-capture mechanisms in the fragmentation of CO upon slow ion-molecule collisions

Abstract

We present a recoil ion—projectile ion coincidence study on the three body fragmentation of $\mathrm{CO_2^{3+}}$ ion into $\mathrm{C^+ + O^+ + O^+}$ fragments upon impact with $\mathrm{Ar^{3+},~Ar^{6+}~and~Ar^{8+}}$ projectile ions having the same velocity of $v_p = 0.49$ a.u. (atomic units) using the recoil ion momentum imaging technique. The kinetic energy release (KER) distributions are presented and the effect of different electron-capture associated processes such as pure capture, electron capture followed by target-ionization or projectile auto-ionization is discussed based on the analysis of KER corresponding to different final projectile charge states post-collision. As the capture stabilization increased, the relative yields in the KER distribution are found to decrease in the high KER side for low charged $\mathrm{Ar^{3+}}$ impact, while an increase is observed for $\mathrm{Ar^{6+}~and~Ar^{8+}}$ impacts. We discuss the interplay between electron-capture, projectile auto-ionization, and target ionization for the dominance of a particular process. We also observe a low-KER feature around 15 eV which was observed for electron and proton impacts, that has not yet been observed for highly charged ion impacts.

Keywords

• KER
• electron capture
• highly charged ion
• molecular fragmentation
• potential energy curves