Scaling behavior of cross-sections for electron-impact multiple-ionization of negatively-charged fullerene ions

Absolute cross-sections for the electron-impact multiple-ionization of mass-selected negatively charged fullerene ions Cn−→Cnq+ (n=60, 70, 84; q=1, 2, 3) have been measured for the first time. A scaling law has been observed for the magnitude of the cross-sections that is a function of the fullerene size n and the charge state q of the product ion. The data indicate that different mechanisms account for the detachment of the extra electron from the negatively charged fullerene and the formation of a positively charged ion, respectively. Moreover, the multiple-ionization of a fullerene anion is found to be a sequential process.