Studies of the Few-Body Problem in Atomic Break-Up Processes

Fully differential studies of single ionization of neutral atoms by charged particle impact have proven to be extremely powerful to advance our understanding of the few-body dynamics in atomic processes. Until a few years ago, such data were only available for electron impact and were mostly limited to electrons ejected into the scattering plane. when fully differential data were finally obtained for ion impact covering the entire three-dimensional space, very surprising features were observed. It then became clear that our understanding of ionization processes in atomic collisions is not nearly as complete as previously assumed. Here, we review the development of experimental and theoretical studies of three-dimensional fully differential single ionization cross-sections since then.