[1] NASA, Ames Res Ctr, Eloret Corp, Stanford, CA 94305 USA
[2] NASA, Ames Res Ctr, Nanotechnol Branch, Moffett Field, CA 94035 USA
[3] Cornell Univ, Atom & Solid State Phys Lab, Ithaca, NY 14853 USA
[4] CNRS, F-75005 Paris, France
[5] Univ Paris 06, Theoret Chem Lab, F-75005 Paris, France