COLLISIONAL PROBES AND POSSIBLE STRUCTURES OF LA2C80

The soluble molecule La2C80 recently reported by Alvarez et al. exhibits a robustness similar to other fullerenes. It survives intact for almost-equal-to 10(-6) s following impact against solid surfaces Si(100) at up to 200 eV, yielding an estimate E(f)>4 eV for fragmentation processes. The high threshold for electron emission suggests that the electron affinity in La2C80- is significantly larger than in C60. These facts seem to rule out an external site for either La atom and disfavor a network-site interpretation, and thus favor endohedral (encapsulation) sites. Among the possible cages, the I(h)-C80 fullerene appears to be highly favorable for the oxidation state (La3+)2C80(6-).