Formation of Dianions in Helium Nanodroplets.

The formation of dianions in helium nanodroplets is reported for the first time. The fullerene cluster dianions (C60) n2− and (C70) n2− were observed by mass spectrometry for n≥5 when helium droplets containing the appropriate fullerene were subjected to electron impact at approximately 22 eV. A new mechanism for dianion formation is described, which involves a two-electron transfer from the metastable He− ion. As well as the prospect of studying other dianions at low temperature using helium nanodroplets, this work opens up the possibility of a wider investigation of the chemistry of He−, a new electron-donating reagent. [ABSTRACT FROM AUTHOR]