Field enhanced dielectronic recombination of Si11+ and C14+ ions

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