High-Energy Collisions of Fullerene Radical Cations with Target Gases: Capture of the Target Gas and Charge Stripping of C₆₀^.+, C₇₀^.+, and C₈₄^.+

This is a paper on the comprehensive study of the products formed when C₆₀ and C₇₀ radical cations undergo high-energy collisions with noble gases and with D₂, N₂, NO, or O₂. A new design four-sector tandem mass spectrometer was used to prove that, as a result of collisions, small target gases are incorporated into intact fullerene radical cations. For helium target gas, the endohedral complexes C₆₀He^.+, C₇₀He^.+, and C₈₄He_.+ are produced directly from the radical cation precursor, and C₆₀He₂^.+ is produced from C₇₀^.+ colliding with He. The molecular gas D₂ also associates with C₆₀^.+ in a high-energy collision. The kinetic energies for product ions resulting from capture of a target gas are derived and compared with experimental values to probe the mechanism of formation of the He-containing and D₂-containing fullerene product ions. The complex formed by capture of the He (or D₂) fragments to produce the majority of the lower mass product ions, both those that contain and those that do not contain the target gas. The internal energy of these complexes was varied by changing the center-of-mass collision energy, which is entirely converted to internal energy of the complex when the target gas is captured. More extensive fragmentation occurs when neon is used as a target gas, and Ne-containing product ions are also observed. Collisions of C₆₀^.+ precursor ions with argon result in the formation of product ions corresponding formally to loss of odd-carbon fragments from C₆₀Ar^.+ to produce, for example, C₅₅Ar^.+. Collisions with the gases N₂, NO, and O₂ yield dramatically enhanced abundances of the doubly charged fullerene ions, thus facilitating the measurement of the second ionization energy by charge-stripping experiments. The work presented here builds on a preliminary communication¹ of these results.