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

Absolute cross-sections for the electron-impact multiple-ionization of mass -selected negatively charged fullerene ions C-n(-) --> C-n(q+) (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 i ndicate that different mechanisms account for the detachment of the extra e lectron from the negatively charged fullerene and the formation of a positi vely charged ion, respectively. Moreover, the multiple-ionization of a full erene anion is found to be a sequential process. (C) 2000 Published by Else vier Science B.V. All rights reserved.