Electron-impact ionization and recombination of atomic ions studied at storage rings

The combination of accelerator technology and merged-beams techniques in storage ring experiments has opened up new experimental opportunities for electron-ion collision studies. In particular, charge changing electron-ion interactions at energies reaching from keV down to μeV with meV (and lower) electron beam temperatures have become accessible with ions of almost all charge states between H- and U92+. Examples of recombination and ionization measurements are presented and specific issues such as interference effects, high-resolution spectroscopy and rate enhancements in the presence of external fields are discussed