The ${\mathrm{C}}_2$ fragmentation of fullerene ions ${\mathrm{C}}_{60}^{q+}$ $(q=1,2,3\mathrm{})$ induced by electron impact was studied for the first time. The cross sections for the loss of a ${\mathrm{C}}_2$ fragment indicate the presence of two different processes. At low electron energies the projectile electron leads to the direct excitation of the giant plasmon resonance. At electron energies larger than 100 eV the fragmentation of the fullerene ions can be described as an unsuccessful ionization. Only this second part of the cross section shows a dependence on the charge state $q$ of the precursor ion.

• Received 19 June 2000

DOI:https://doi.org/10.1103/PhysRevLett.85.3604