Recombination of U92+ ions with electrons

Recombination of fully stripped U92+ ions with electrons has been investiga ted at the Experimental Storage Ring (ESR) in Darmstadt. Absolute recombina tion rate coefficients have been measured for relative energies from 0 to 3 3 eV. For energies greater than 20 meV the experimental result is well desc ribed by the theory for radiative recombination (RR). Below 20 meV the expe rimental rate increasingly exceeds the RR calculation as observed previousl y in the recombination of light bare ions as well as of Bi83+. This low-ene rgy rate enhancement is shown to scale as Z(2.6) for bare ions, where Z is the atomic number of the ion. The U92+ recombination rate enhancement is in sensitive to changes of the electron density. Variation of the magnetic gui ding field strength from 80 mT to 120 mT resulted in oscillations of the re combination rate at 0 cV. The oscillations are partly attributed to changes of the transverse electron temperature accompanying the change of the magn etic guiding field strength; partly they may be caused by uncompensated sma ll changes of the interaction angle between the two beams.