Selective formation of C20 cluster ions by field evaporation from carbon nanotubes

Carbon cluster ions generated by field evaporation from single-walled nanotubes and multi-walled nanotubes have been analyzed by mass spectrometry. The observed mass spectra showed that the singly charged C20 clusters, C20+, were selectively generated as magic clusters for both SWNTs and MWNTs. The onset evaporation field of C20+ was estimated to be about 10 V nm−1. The specific number of atoms comprising the magic cluster indicates a dodecahedral structure instead of a linear chain or a ring.