Absolute cross sections have been measured for the first time for the electron-impact single ionization of the fullerene ions ${\mathrm{C}}_{60}^{+}$, ${\mathrm{C}}_{60}^{2+}$, ${\mathrm{C}}_{60}^{3+}$, and ${\mathrm{C}}_{70}^{+}$ as well as for double ionization of ${\mathrm{C}}_{60}^{+}$ ions at electron energies ranging from threshold up to 1000 eV. It is found that the cross sections ${\mathrm{\sigma }}_{1,2}$ for ${\mathrm{C}}_{60}^{+}$ and ${\mathrm{C}}_{70}^{+}$ ions coincide within error bars and, furthermore, that at energies greater than 60 eV the cross section ${\mathrm{\sigma }}_{2,3}$ for ionization of ${\mathrm{C}}_{60}^{2+}$ ions is larger than ${\mathrm{\sigma }}_{1,2}$. In addition, cross sections for fragmentation ${\mathrm{C}}_{60}^{+}$→${\mathrm{C}}_{56}^{+}$ and for fragmentation ionization ${\mathrm{C}}_{60}^{+}$→${\mathrm{C}}_{56}^{2+}$ are presented.

• Received 2 August 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.3439