Experimental Search and Characterization of Icosahedral Clusters: A112X- (X=C, Ge, Sn, Pb)

Photoelectron spectra of Al12X (X= C, Ge, Sn, Pb) were measured to probe the electronic structure of Al12X. These clusters, all possessing 40 valence electrons, were expected to be magic numbers with Ih-X(at)Al12 structures, closed electron shells, and large energy gaps. We showed that for X=Ge, Sn, and Pb that was indeed the case, although non-Ih isomers were also observed. The energy gaps of the three Ih-XAl12 species range from 1.1 to 1.3 eV. The spectra of Al12C- were distinctly different from the other species, confirming that it does not possess an icosahedral structure