Electron-ion recombination using the modified cryring electron cooler

Abstract Recent electron-ion recombination experiments at the heavy-ion syncrotron storage ring CRYRING are described. These experiments include state selective radiative recombination into mid- n levels of deuterons and dielectronic recombination of Ar 13+ . Modifications to the CRYRING electron cooler have reduced the transverse electron temperature to a few tenths of an meV/ k B . The ultrahigh energy resolution achieved is demonstrated in the recent experiments. The widths of the Ar 13+ Δn = 0 dielectronic recombination resonances are resolved to 30 meV FWHM. Detailed calculation of the electron-ion interaction energies has allowed a determination of the peak positions to ± 30 meV.