Measured appearance energies of C⁺ _n (3 ≤ n ≤ 10) fragment ions produced by electron impact on C₆₀

We have used mass spectrometric techniques to determine the appearance energies for the formation of small, singly charged C⁺_n fragment ions (3 ≤ n ≤ 10) produced by controlled electron impact on C₆₀ under single collision conditions. The measured appearance energies range from 79 eV (C⁺₃) to 91 eV (C⁺₁₀) and show, within the experimental error bar of ±5 eV, little variation with the cluster size. This result is distinctly different from the behaviour of the previously measured appearance energies for the large fragment ions C⁺₅₈ to C⁺₄₄ and indicates that the small fragment ions are the result of a different fragmentation pathway.