Formation and coalescence of fullerene ions from direct laser vaporization

Abstract

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.