Formations of Dumbbell ${\mathbf{C}}_{118}$ and ${\mathbf{C}}_{119}$ inside Clusters of ${\mathbf{C}}_{60}$ Molecules by Collision with $\alpha$ Particles

We report highly selective covalent bond modifications in collisions between keV alpha particles and van der Waals clusters of ${\mathrm{C}}_{60}$ fullerenes. Surprisingly, $\mathrm{C}_{119}{}^{+}$ and $\mathrm{C}_{118}{}^{+}$ are the dominant molecular fusion products. We use molecular dynamics simulations to show that $\mathrm{C}_{59}{}^{+}$ and $\mathrm{C}_{58}{}^{+}$ ions—effectively produced in prompt knockout processes with ${\mathrm{He}}^{2+}$—react rapidly with ${\mathrm{C}}_{60}$ to form dumbbell $\mathrm{C}_{119}{}^{+}$ and $\mathrm{C}_{118}{}^{+}$. Ion impact on molecular clusters in general is expected to lead to efficient secondary reactions of interest for astrophysics. These reactions are different from those induced by photons.