Electron interaction with S6-C60(CF3)12: Energy pool of fullerene cage

Electron impact study of isomer S6-C60(CF3)12 resulted in the ionization efficiency curves (IEC) of singly and doubly charged positive ions and electron capture resonances for negative ones. The appearance energy (AE) values of the fragment C60(CF3)n ions appear to correlate linearly with n down to n = 0 (C60 ion) and its value for each additional act of CF3 detachment rises by 2-3 eV. Observations of metastable ions reveal several cases of quasi-simultaneous detachment of two CF3-groups. Energy shift between ionization energy of S6-C60(CF3)12 and AE of the first fragment C60(CF3)11 ion was observed as 8.8 eV for singly and 8.3 eV for doubly charged ions. To rationalize this energy shift a DFT calculation of the orbital energies for the C60(CF3)12+ cation have been carried out and energy gap between HOMO and LUMO orbitals was estimated. High probability of occupation of the localized σ* orbital and CF3-elimination require four electron excitation and can be effected via a multielectron transition from the multitude of the densely distributed occupied π orbitals. The analogies with the fragmentation of C60 with C2-elimination are mentioned.