Collisional Formation of Metallofullerenes

Metallofullerenes are synthesized by bombarding C60 with alkali metal ions. Two different approaches are used: Ion implantation into a film of fullerenes, and gas-phase collisions. The film is grown by vapor deposition onto a rotating target; metal ions produced by surface ionization are co-implanted during film growth. A pulsed laser beam subsequently desorbs and ionizes the material into a time-of-flight mass spectrometer. The relative yield of NaC60 ions reaches 37 % at an implantation energy of 100 eV. In another experimental approach, a metal ion beam is crossed with a thermal beam of fullerenes; metallofullerene and fullerene product ions are identified in the mass spectrometer. Our results (relative yields, appearance energies, breakdown energies) deviate significantly from those reported by other authors