Collisional fragmentation of Ar@C₆₀

The fragmentation patterns resulting from collisions between (Ar@C₆₀)⁺ or (Ar@C₆₀)^- ions and H₂, He, CH₄, Ne, Ar and Kr target gases have been measured. The ion-source material Ar@C₆₀ was synthesized by heating C₆₀ under 3000 atm of argon gas, leading to a 10^-3 concentration of endohedral fullerenes. The fragmentation spectra (charged molecules only) are dominated by positive ions both when positive or negative endohedrals break up. Endohedral fragment ions Ar@C_n⁺ (48≤n≤60) as well as all carbon fragments are observed. For collisions involving (Ar@C₆₀)^-, ejection of the Ar atom together with two electrons, without permanently damaging the fullerene cage, is a prominent reaction channel, indicating that a 'window' or a deformation in the form of e.g. a large hole, through which the argon atoms can exit, is opened during the collision.