The observation of sequential attachment of two electrons to the ${\mathrm{C}}_{84}$ molecule and the subsequent autodetachment of the ${\mathrm{C}}_{84}$ dianion is reported. Remarkably, the cross section for attaching the second electron is estimated to be of the same order as that for adding the first electron. The measured lifetime for autodetachment of ${\mathrm{C}}_{84}^{-2\mathrm{}}$ $\left(\sim 60\mu \sec \right)$ is in accord with calculations assuming “thermionic emission” from the vibrationally hot dianion. The first $\left({\mathrm{EA}}_1\right)$ and second $\left({\mathrm{EA}}_2\right)$ electron affinities of the two low-lying $D_2$ and $D_{2d}$ isomers of ${\mathrm{C}}_{84}$ are calculated using density functional theory to be $+3.14\mathrm{}$ and $+0.44\mathrm{eV}$, respectively.

• Received 9 December 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.4367