A COLLISIONAL STUDY OF SOME C60 AND C70 FULLERENE IONS

The high-energy collision-induced dissociation (CID) mass spectra of C60+, C70+, C60(2+), C70(2+) and C60(3+) are reported. In all cases, fragmentation occurs by loss of an even number of carbon atoms, in agreement with photodissociation studies of C60+ and C70+. No charge-separation reactions are observed for the multiply charged ions. Collision-induced dissociation of C60+ leads to a slight preference for formation of C50+, while dissociation of C70+ and C70(2+) shows a more pronounced preference for formation of C60+ and C60(2+), respectively. Under electron-capture chemical-ionization conditions the fullernes readily capture an electron to form the molecular anions. Collision-induced dissociation of C60- and C70- leads to elimination of 1, 2 and 4 carbon atoms; the elimination of one carbon is unique among larger carbon cluster ions. Charge inversion of the molecular anions leads to formation of the respective molecular cations and fragmentation of these cations by loss of an even number of carbon atoms. Formation of C50+ is slightly preferred in the C60- case, while C60+ is the most abundant ion in the charge inversion mass spectrum of C70-.