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An experimental technique is investigated to separate/enrich fullerenes of metallofullerenes, exploiting differences in sublimation temperatures without the use of solvents. Fullerenes are sublimed out of the soot and deposited on a quartz rod along a temperature gradient (gradient sublimation). In a position-sensitive experiment the composition of the deposit on the rod is monitored by laser-desorption mass spectrometry. Strongly enriched regions containing specific fullerene molecules (i.e., C[sub 84] or LaC[sub 82]) are observed. Furthermore, C[sub 74], which could not be extracted from the soot by organic solvents, sublimes out of the soot. 26 refs., 6 figs.

Surface collisions of negatively charged atomic clusters C N - and Si N - , N

The authors report the formation of fullerenes from graphite by sputtering and electron beam evaporation. Under conditions that differ dramatically from those in the previously known fullerene production processes, the new methods preferentially yield the soluble higher fullerenes C{sub 70}, C{sub 76}, C{sub 78}, and C{sub 84} in addition to minor amounts of C{sub 60} only. Upon passage of carbon particles formed by electron beam evaporation through an electrostatic field, fullerenes are mainly isolated from the cathode, not from the anode, which supports the formation of cationic intermediates in fullerene growth mechanisms. The variables thought to be important for fullerene production can be controlled efficiently in the new processes. 18 refs., 3 figs.

The technique of carbon-arc evaporation has been successfully utilized to encapsulate a wide variety of rare-earth species in carbon cages. The authors have observed M{sub m} @ C{sub n} (M = Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, or Er) species present in the toluene extracts of the carbon soot using laser desorption mass spectrometry. The presence of multiple-metal species appears to depend strongly on the metal-to-carbon atom ratio found in the starting rods, with the higher metal concentrations favoring multiple-metal incorporation. One often observed dimetallofullerene is M{sub 2}{degrees}C{sub 80}. Molecular orbital arguments are presented to support a possible icosahedral structure for C{sub 80}. 27 refs., 2 figs., 1 tab.