Abstract. The enhancement of dielectronic recombination of multiply charged ions by external electric fields has been studied under controlled conditions. The heavy ion storage rings CRYRING at Stockholm University and the heavy ion storage ring TSR at the Max-Planck-Institut in Heidelberg were used to store beams of Si¹¹⁺ (ion energy 280 MeV) and Cl¹⁴⁺ (ion energies 250 MeV and 110 MeV), respectively. Recombination in the electron cooler has been measured over energy ranges covering all resonances due to 2s → 2p core exitation. External electric fields up to 183 V/cm at CRYRING and up to 379 V/cm at the TSR have been applied. In the TSR experiment the influence of different magnetic guiding fields as well as the influence of different electron densities in the electron cooler on the recombination rate was investigated. A significant rate enhancement was found for 1s²2pnl Rydberg resonances with n > 25 for Si¹¹⁺ ions and n > 20 for Cl¹⁴⁺ ions.

PACS number: 34.80.Lx

Received 14 September 1998