Electron attachment to doped helium droplets: C60 -, (C60)2 -, and C60D2O- anions

Helium nanodroplets, formed in a supersonic expansion, are doped with C₆₀ in a pickup cell. In some experiments, they are co-doped with water. Electrons are attached to the doped droplets; the yield of anions is recorded as a function of electron energy. The C₆₀ ^- yield extends to much higher energies than in experiments involving isolated, hot fullerenes; we attribute the difference to the low temperature of the neutral precursors and the efficient cooling of the nascent anions by the helium droplet, which quench thermally activated autodetachment. The yields of (C₆₀)₂ ^- and C₆₀D₂O^- anions reveal another important factor, namely depletion of the anion signal by dissociation which is energetically more facile than autodetachment.