Fragmentation dynamics of CO24+ : Contributions of different electronic states

Abstract

Fragmentation of ${\mathrm{CO}}_{2}^{4+}$, created by the impact of slow, highly charged ions $(96 \mathrm{keV} {\mathrm{Ar}}^{q+};$ $8\ensuremath{\le}q\ensuremath{\le}14)$ on ${\mathrm{CO}}_{2}$, has been studied by recoil ion momentum spectrometry. ${\mathrm{CO}}_{2}^{4+}$ was found to dissociate into three ionic fragments through two channels: ${\mathrm{CO}}_{2}^{4+}\ensuremath{\rightarrow}{\mathrm{O}}^{+}+{\mathrm{C}}^{2+}+{\mathrm{O}}^{+}$ [the (1,2,1) channel] and ${\mathrm{CO}}_{2}^{4+}\ensuremath{\rightarrow}{\mathrm{O}}^{2+}+{\mathrm{C}}^{+}+{\mathrm{O}}^{+}$ [the (2,1,1) channel]. The kinetic energy of each fragment ion and the total kinetic energy release (KER) distributions for these channels were derived. Ab initio quantum chemical calculations at the multiconfiguration self-consistent-field configuration-interaction level of theory were carried out to obtain the potential energy curves of ${\mathrm{CO}}_{2}^{4+}$, from which the expected KER values were derived. A comparison of the experimental KER distributions with the expected KER values for different excited states enabled the estimation of the relative probabilities of accessing different electronic states of ${\mathrm{CO}}_{2}^{4+}$. These probabilities were found to depend on the projectile charge $q$. The fragmentation was visualized using the Dalitz plots, which revealed that the (1,2,1) channel arises exclusively via concerted fragmentation, while the (2,1,1) channel also has a small contribution from sequential fragmentation.