Dissociative ionization of OCS induced by highly charged ion impact

Abstract

Dissociation of $\mathrm{OC}{\mathrm{S}}^{q+}$ $(q=3--7)$ produced by $18\text{\ensuremath{-}}\mathrm{keV}/\mathrm{u}\phantom{\rule{0.16em}{0ex}}{\mathrm{Ne}}^{8+}$ ion impact has been investigated using recoil ion momentum spectroscopy. Ten complete three-body Coulomb fragmentation channels were analyzed. Scattered projectile charge state $({\mathrm{Ne}}^{7+} \mathrm{or} {\mathrm{Ne}}^{6+})$ differentiated branching ratios and the kinetic-energy release (KER) distributions were analyzed for different fragmentation channels. Through Dalitz plots, Newton diagrams, and native frames, we have studied the concerted and sequential fragmentation mechanisms for channels leading to ${\mathrm{O}}^{+}+{\mathrm{C}}^{+}+{\mathrm{S}}^{+}$, ${\mathrm{O}}^{+}+{\mathrm{C}}^{+}+{\mathrm{S}}^{2+}$, ${\mathrm{O}}^{2+}+{\mathrm{C}}^{+}+{\mathrm{S}}^{+}$, and ${\mathrm{O}}^{+}+{\mathrm{C}}^{+}+{\mathrm{S}}^{3+}$. For concerted dissociation mechanisms, the molecular bending fragmentation dominates in these channels. For sequential dissociation mechanisms, the KER distribution for the dissociation of intermediate ions $\mathrm{C}{\mathrm{O}}^{2+}/\mathrm{C}{\mathrm{S}}^{2+}$ were determined and the rotation of the intermediate molecular ion $\mathrm{C}{\mathrm{O}}^{2+}$ before the second step dissociation was discussed. Thereby the relative branching ratios of events coming from sequential versus concerted mechanism were also estimated.