Enhancement effects on electron-ion recombination rates

Recombination of highly charged ions with electrons is studied by accelerator based merged-beams experiments. In most measurements excessively high recombination rates are observed at low relative energies which cannot be explained by ordinary radiative recombination. The enhanced rates lead to serious losses of ions during the electron cooling process in ion storage rings. Another type of rate enhancement, known from previous experiments on dielectronic recombination, is related to external fields in the electron-ion collision region. By introducing controlled electric fields in the cooler of a storage ring it has been possible for the first time to obtain quantitative results for effects of electric fields on dielectronic recombination of highly charged ions.