Emission of singly and doubly charged light fragments fromC60r+(r=4–9)inXe25+−C60collisions

Abstract

Asymmetrical fission of ${\mathrm{C}}_{60}^{r+}$ $(r=4--9)$ ions are studied in ${\mathrm{Xe}}^{25+}\ensuremath{-}{\mathrm{C}}_{60}$ collisions at 100 keV impact energy $(v\ensuremath{\approx}0.18\mathrm{a}.\mathrm{u}.).$ The branching ratios for the emission of a singly or a doubly charged light fragment, ${\mathrm{C}}_{m}^{+}$ or ${\mathrm{C}}_{m}^{2+},$ are measured for each initial charge state r. The measured m-dependent branching ratios for the singly charged ${\mathrm{C}}_{m}^{+}$ fragment emission channels are reproduced using a simple statistical model. The ionization energies $I({\mathrm{C}}_{60\ensuremath{-}2n}^{q+})$ for even numbered fullerenes ${\mathrm{C}}_{60\ensuremath{-}2n}^{q+}$ $(q=1--5,8;n=1--4)$ and $I({\mathrm{C}}_{2n}^{+})$ for singly charged light fragments ${\mathrm{C}}_{2n}^{+}$ $(n=1--4)$ are estimated by the density-functional theory. The total branching ratio for the ${\mathrm{C}}_{m}^{2+}$ emission channels is found to increase from less than 2 to 25% when the charge r of the parent ion ${\mathrm{C}}_{60}^{r+}$ increases from 5 to 9.