Ionization and fragmentation of fullerene ions by electron impact

Absolute cross sections for the electron-impact multiple ionization and fra gmentation of negatively charged fullerene ions C-n(-) (n = 60, 70, 84) --> C-n-m(q+) (q = 1, 2, 3 and m = 0, 2, 4) have been measured for electron en ergies up to 1 keV A scaling law has been observed for the magnitude of the ionization cross sections. Furthermore, the multiple ionization of a fulle rene anion is found to be a sequential process. A novel ionization mechanis m is proposed which can be expected to be valid also for other negatively c harged molecular or cluster ions.