[1] Univ Sussex, CPES, Fullerene Sci Ctr, Brighton BN1 9QJ, E Sussex, England
[2] Univ Nacl Autonoma Mexico, Inst Fis, Queretaro 76000, Mexico
[3] Max Planck Inst Met Res, D-70174 Stuttgart, Germany
[4] Univ Calif Santa Barbara, Mat Res Lab, Santa Barbara, CA 93106 USA