Thermally induced structural transition in (C60)n clusters

Both neutral and charged (C60)n clusters were heated to temperatures at which they evaporated molecules. Particularly stable clusters resisted evaporation and manifested themselves as enhanced peaks in the mass spectra. At 490 K, the set of enhanced mass peaks (e.g., n=13, 19, 39, 46, 49, 55, 116, 131, 147) indicated the presence of icosahedral structures. A different set of intense peaks (e.g., n=38, 48, 58, 68, 71, 75, 77, 84, 98) dominated the mass spectra at temperatures near 585 K. The new set correlates rather well with that expected for close-packed and decahedral structures. The two sets of enhanced peaks were found to be independent of the cluster charge at all temperatures investigated.