Association between projectile and target excitation in slow Ar$^{q+}$-CO$_2$ collisions

TL;DR

This study explores how projectile and target excitations are correlated in slow Ar$^{q+}$-CO$_2$ collisions, revealing charge-dependent differences in kinetic energy distributions and the role of multielectron capture.

Contribution

It provides new insights into the relationship between projectile autoionization and target excitation, supported by classical over-the-barrier model calculations.

Findings

KERD shape varies with charge transfer (elta q)

Higher projectile charge reduces differences in KERD

Strong correlation between target excitation and projectile autoionization

Abstract

We investigate ionic fragmentation of CO$_2^{n+}$~\mbox{($2\le n\le 4$)} produced in collisions with Ar$^{q+}$~\mbox{($4\le q\le 16$)} projectiles at a collision velocity of $\approx$~0.3~a.u. For most projectile and fragmentation channel combinations, the shape of the kinetic energy release distribution (KERD) differs with the electron capture mediated charge change (\mbox{$\Delta q$}) in the scattered projectile: KERD for \mbox{$\Delta q = 2$} is broader at high KER than for \mbox{$\Delta q =1$}. The difference generally diminishes with increasing projectile charge. Two deviations in this general trend are seen in the fragmentation of CO$_2^{3+}$, one for Ar$^{4+}$ impact in the high KER region and the other for Ar$^{6+}$ impact in the low KER region. The calculated reaction windows for multielectron capture within the framework of the extended classical over-the-barrier model (ECOBM) indicate that while ionization of the target occurs via multielectron capture, the scattered projectile may subsequently undergo multi-fold autoionization. Interpreting projectile autoionization to be a consequence of capture into highly excited states and high fragment KER to be a consequence of excitation of the ionized target to high-lying states, we find a strong dependence between the target and scattered projectile excitations.