DIELECTRONIC RECOMBINATION OF AR13+ AT CRYRING

We have investigated Delta n = 0 dielectronic recombination resonances of Ar13+ at CRYRING. The Ar13+ ions were obtained from the electron b eam ion source CRYSIS. The ultracold electron beam produced in the mod ified electron cooler was used as the electron target, resulting in re sonance widths less than 30 meV FWHM. Determination of the observed re sonance line energies, which requires transformation from laboratory t o center of mass frame, includes acceleration of the ion beam due to t he drag force encountered as the electron energy is scanned. With this transformation the uncertainty in absolute line positions has been re duced to less than 30 meV.