Formation and coalescence of fullerene ions from direct laser vaporization

A series of carbon cluster ions have been created by direct laser vaporization of elementary carbons and organic compounds with different structures and compositions. The mass spectra of the carbon cluster ions were recorded in situ by a time-of-flight mass spectrometer and the experimental results showed that the formation of fullerenes and their relative abundances are closely related to the surface structure of the sample. Under direct laser vaporization, the products from a perfect (0001) surface of graphite were mainly C60 and C70. The surface perpendicular to the (0001) plane of graphite could not produce C60, other fullerene ions or compounds containing six-membered aromatic carbon rings. The products of amorphous carbon and aromatic compounds included C60 and other fullerenes, among which those with a mass twice that of C60 were most abundant. Furthermore, C60 and C70 could also be aggregated from direct laser vaporization. Based on these experimental results, mechanism for formation of C60 and other fullerenes is suggested.