IONIZATION AND FRAGMENTATION OF FULLERENE IONS BY ELECTRON-IMPACT

Absolute cross sections have been measured for the first time for the electron-impact single ionization of the fullerene ions C60+, C-60(2+), C-60(3+), and C70+ as well as for double ionization of C60+ ions at electron energies ranging from threshold up to 1000 eV. It is found that the cross sections sigma1,2 for C60+ and C70+ ions coincide within error bars and, furthermore, that at energies greater than 60 eV the cross section sigma2,3 for ionization of C-60(2+) ions is larger than sigma1,2. In addition, cross sections for fragmentation C60+ --> C56+ and for fragmentation ionization C60+ --> C-56(2+) are presented.