Introduction and Preliminary Remarks

The single ionization of an atom, i.e. the emission of a bound electron, by impact of ions or photoabsorption belong to the basic phenomena studied by atomic physics and can reveal insights into the structure of the atom as well as the interaction dynamics of the atom with its environment upon ionization. These well-known processes (for ion impact ionization see, e.g. [1–4] and references therein and for photoionization see, e.g. [5–8] and references therein) have been considered for a wide range of incident energies and, still today, there is great interest in further improving theoretical descriptions and experimental techniques.