COLLISION OF LI+ AND NA+ WITH C60 - INSERTION, FRAGMENTATION, AND THERMIONIC EMISSION

Interactions of Li+ and Na+ with C60 molecules have been studied over the collision energy range from 0 to 150 eV. We observe insertion of the alkali-metal ions to form the endohedral [LiC60]+ and [NaC60]+ species, with energy thresholds of 6 and 20 eV, respectively. At higher collision energies, the excited [NaC60]+ appears to relax mainly by loss of C2 units from the fullerene cage, yielding [NaC60-2n]+. For [LiC60]+, escape of the Li+ competes effectively with C2 loss. For both Li+ and Na+, signal for pure carbon fragment ions C60-2n+ increases sharply at approximately 30 eV, which is attributed to thermionic emission.