Electron interaction with S 6-C 60(CF 3) 12: Energy pool of fullerene cage

Abstract

Electron impact study of isomer S 6-C 60(CF 3) 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 C 60(CF 3) n ions appear to correlate linearly with n down to n = 0 (C 60 ion) and its value for each additional act of CF 3 detachment rises by 2–3 eV. Observations of metastable ions reveal several cases of quasi-simultaneous detachment of two CF 3-groups. Energy shift between ionization energy of S 6-C 60(CF 3) 12 and AE of the first fragment C 60(CF 3) 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 C 60(CF 3) 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 CF 3-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 C 60 with C 2-elimination are mentioned.