Collisions of cold electrons with cooled ions in CRYRING

We have studied collisions of electrons with ion at very low energies and obtained recombination rate coefficients as well as high precision spectroscopic data. The low collision energies were reached with the upgraded electron cooler in the storage ring CRYRING at Manne Siegbahn Laboratory in Stockholm. With the cooled beams, the mean relative energy between electrons and ions could be varied from 10-6 eV to ∼ 100 eV. Experimental data are reported for bare ions and compared with calculations for radiative recombination process. Here, the measured rate coefficients are found systematically higher than theoretical predictions. Examples of high resolution measurements of dielectronic recombination resonances are presented here for the Li-like ions F +6 and Ar15+ and compared to many-body theories of the electron-ion interaction. (authors)