Distinction between multicharged fullerene ions and their fragment ions with equal charge-to-mass

Optical Spectroscopy of Small Carbon Clusters from Electron-Impact Fragmentation and Ionization of Fullerene-C60

A series of cationic molecular fragments (C _n⁺, n = 11, 12, 15, 16, 18, and 21), produced by electron-impact ionization of C₆₀ in the gas phase, were each mass-selected and accumulated in cryogenic Ne matrices. Optical absorption measurements in the UV-vis and IR spectral ranges reveal linear carbon chain structures. In particular, we have observed the known electronic transitions of linear C₁₁, C₁₅, and C₂₁. The NIR transitions of linear C₁₅^-, C₁₆^-, and C₁₈^- have also been detected, indicating that soft-landing of the corresponding cations can also involve charge-changing. Newly observed electronic absorptions at 410.3 and 429.9 nm have been assigned to linear C₁₈ absorptions at 438.2, 443.5, 422.3, and 433.7 nm, to linear C₁₅⁺, and absorption at 395.5 nm, to linear C₁₆. Increasing deposition energy leads to fragmentation upon impact. This is indicated by absorptions of C₁₀ (313, 316.3 nm), when depositing C _n⁺ ( n = 11, 15, 16) as well as C₁₂ (332 nm) or C₁₄ (347.4, 356.6 nm), when depositing C₁₅⁺ or C₁₆⁺, respectively. These were previously assigned to cyclic isomers. We reassign them to linear isomers here on the basis of plausibility arguments. The observations have been supported by time-dependent density functional theory calculations for ring and chain isomers of C _n^+/-/0, 10 ≤ n ≤ 20 up to the vacuum-UV range. The electronic absorptions of carbon chains are at least 1 order of magnitude stronger than all NIR electronic absorptions of C₆₀⁺, which have recently been attributed to several of the diffuse interstellar bands. Considering that fullerene multifragmentation yields long carbon chains that have very strong absorptions both in the UV-vis and IR spectral regions, these systems appear to be good candidates to be observed in regions of space containing fullerenes.

A study on electron impact mass spectrometry of epoxy methylated fullerenols

Mass spectra of the epoxy methylated[60]fullerenols were obtained by EI mass spectrometry using "desorption" or "in-beam" technique. The mass spectra have an intense molecular monocation peak M(+) and a weak dication peak M(++), revealing the stability of these products under the MS (EI) conditions. The remaining peaks correspond to the successive loss of methyl groups and oxygen atoms for which the pure fullerene represents a more stable product. The distinction between the multiply charged fullerene C(60)(z+) and their fragments with equal m/z was also studied.