Recombination of bare Bi83+ ions with electrons

Electron-ion recombination of completely stripped Bi83+ was investigated at the Experimental Storage Ring (ESR) of the Gesellschaft fur Schwerionen-forschung (GSI) in Darmstadt, Germany. It was the first experiment of this kind with a bare ion heavier than argon. Absolute recombination rate coefficients have been measured for relative energies between ions and electrons from 0 up to about 125 eV. In the energy range from 15 meV to 125 eV good agreement is found between the experimental result and theory for radiative recombination (RR). However, below 15 meV the experimental rate increasingly exceeds the RR calculation and at E-rel = 0 eV it is a factor of 5.2 above the expected value. A variation of the electron density by a factor of 3 had no significant influence on the recombination rate which is in agreement with other experiments. An additional variation of the magnetic guiding field of the electrons from 70 mT to 150 mT in steps of 1 mT resulted in periodic oscillations of the rate which are accompanied by considerable changes of the transverse electron temperature.