Excited states of multiply-charged anions probed by photoelectron imaging: riding the repulsive Coulomb barrier.

Many properties of isolated multiply-charged anions (MCAs) are dictated by the strong intra-molecular Coulomb interactions that are present. The most striking property of MCAs is a long-range repulsive Coulomb barrier (RCB) that arises from the repulsive interaction between an electron and an anion which must be overcome to form a MCA. Excited states provide a route to probing this RCB and the focus of this Perspective is on recent photoelectron experiments, including angularly and temporally resolved, that have provided detailed physical insight into the RCB surfaces, their anisotropy, and their use to monitor molecular dynamics in real-time. An outlook provides some future prospects that studies on MCAs provide in terms of monitoring structural, charge-migration, and solvation dynamics.