Doubly charged negative ions via charge-exchange collisions:C60F36−+CH4→C60F36−2+CH4+

Abstract

Studies of electron transfer from a molecule $({\mathrm{CH}}_{4})$ to a negative ion $({\mathrm{C}}_{60}{\mathrm{F}}_{36}^{\ensuremath{-}})$ at low-ion collision energies (4 to 10 keV) are reported. The center-of-mass energy threshold for the reaction ${\mathrm{C}}_{60}{\mathrm{F}}_{36}^{\ensuremath{-}}+{\mathrm{CH}}_{4}\ensuremath{\rightarrow}{\mathrm{C}}_{60}{\mathrm{F}}_{36}^{\ensuremath{-}2}+{\mathrm{CH}}_{4}^{+}$ is found to be \ensuremath{\sim}60 eV, which is well above the estimated thermodynamic endoergicity $[{V}_{i}({\mathrm{CH}}_{4}{)\ensuremath{-}A}_{e}({\mathrm{C}}_{60}{\mathrm{F}}_{36}^{\ensuremath{-}})\ensuremath{\sim}10\mathrm{eV}].$ Dissociative charge transfer to produce ${\mathrm{C}}_{60}{\mathrm{F}}_{35}^{\ensuremath{-}}$ and ${\mathrm{C}}_{60}{\mathrm{F}}_{34}^{\ensuremath{-}}$ is also observed but much less probable. Collisions of other negative ions with neutral molecules (notably ${\mathrm{C}}_{84}^{\ensuremath{-}})$ did not result in a detectable signal of doubly charged negative ions.