Doubly charged negative ions of carbon-60

We report the observation of long-lived (τ>${10}^{\mathrm{-}3}$ sec) doubly charged negative ions of ${\mathrm{C}}_{60}$ in the gas phase. ${\mathrm{C}}_{60}^{\mathrm{-}}$ and ${\mathrm{C}}_{60}^{2\mathrm{-}}$ ions are produced by laser desorption from a surface covered with ${\mathrm{C}}_{60}$ molecules and are believed to be produced by negative surface ionization from the laser-heated surface. Pseudopotential calculations indicate that ${\mathrm{C}}_{60}^{2\mathrm{-}}$ is slightly bound (electron affinity of ${\mathrm{C}}_{60}^{\mathrm{-}}$≃0.1–0.4 eV) relative to ${\mathrm{C}}_{60}^{\mathrm{-}}$.