Bimodal Distribution in the Fragmentation Behavior of Small Antimony ClustersSbx+(x=3–12) Scattered from a Highly Oriented Pyrolitic Graphite Surface

Abstract

The fragment ion-yield curves for the scattering of antimony cluster cations from highly oriented pyrolitic graphite show two clearly separated abundance maxima. On the low-energy side ( $\ensuremath{\le}150\ifmmode\pm\else\textpm\fi{}30\mathrm{eV}$) the interaction is characterized by the unimolecular fragmentation of the clusters and by neutralization as the competing process. The neutralization efficiency reaches a maximum at collision energies of $150\ifmmode\pm\else\textpm\fi{}30\mathrm{eV}$. Above this boundary a transition to two different processes is indicated by a change in the fragment ion distribution. These competing processes are here the shattering and the implantation of the clusters. The threshold for implantation depends significantly on cluster size.