Ions Colliding with Cold Polycyclic Aromatic Hydrocarbon Clusters

Abstract

We report the first experimental study of ions interacting with clusters of polycyclic aromatic hydrocarbon (PAH) molecules. Collisions between 11.25 keV $^{3}\mathrm{He}^{+}$ or 360 keV $^{129}\mathrm{Xe}^{20+}$ and weakly bound clusters of one of the smallest PAH molecules, anthracene, show that ${\mathrm{C}}_{14}{\mathrm{H}}_{10}$ clusters have much higher tendencies to fragment in ion collisions than other weakly bound clusters. The ionization is dominated by peripheral collisions in which the clusters, very surprisingly, are more strongly heated by ${\mathrm{Xe}}^{20+}$ collisions than by ${\mathrm{He}}^{+}$ collisions. The appearance size is $k=15$ for $[{\mathrm{C}}_{14}{\mathrm{H}}_{10}{]}_{k}^{2+}$.