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Molecular anions are of fundamental importance and ubiquitous in many chemical, physical and biological environments. The chemical and physical properties of anions are very different from their neutral or cationic counterparts making them interesting species to study and characterize. While it is straightforward to assert that excited states of the anion play a crucial role in the electron accepting capabilities of the neutral molecules, electronically stable excited states of anions are thought to be scarce at best.

Following an overview of the special characteristic of molecular anions, we shall present our study of the electronically bound spectrum of the anion. Much like the neutral fullerene, the anion possesses certain unique properties which have attracted a great deal of research. One of these special properties, only recently fully uncovered, is that the anion supports a substantial number of electronically stable excited states in contrast to other molecular anions with comparable electron affinity. In this work, we clarify how the anion can support so many stable states by analyzing the radial and angular distributions of the excess electron bound to the anion. The analysis is based on ab initio calculations which are by far the most accurate on the anion to date. Surprisingly, the radial distributions are highly similar for states of very different binding energies and the analysis stresses the importance of angular correlation in binding the excess electron.

We further analyze the effect of the single excess electron on the electrons of the underlying neutral molecule. We demonstrate how this substantially modifies the actual distribution of the excess charge by shifting the underlying electron density. Finally, the effect of the perturbation of the anionic states in the presence of incarcerated atoms within the carbon shell is analyzed and discussed.