Berlin 2001 – wissenschaftliches Programm

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A: Atomphysik

A 19: Electrons, incl. Scattering and Recombination

A 19.5: Vortrag

Freitag, 6. April 2001, 16:45–17:00, H1028

Rate enhancement in the recombination of fully stripped U⁹²⁺ and Bi⁸³⁺ ions with electrons — •W. Shi¹, T. Bartsch¹, S. Böhm¹, C. Böhme¹, C. Brandau¹, A. Hoffknecht¹, S. Kieslich¹, H. Knopp¹, S. Schippers¹, A. Müller¹, C. Kozhuharov², F. Bosch², B. Franzke², P.H. Mokler², M. Steck², Th. Stöhlker², and Z. Stachura³ — ¹Institut für Kernphysik, Universität Giessen, D-35392 Giessen, Germany — ²Gesellschaft für Schwerionenforschung (GSI), D-64291 Darmstadt, Germany — ³Institute for Nuclear Physics, 31-342 Kraków, Poland

Recombination of U⁹²⁺ and Bi⁸³⁺ ions with electrons has been investigated at the Experimental Storage Ring (ESR). Absolute recombination rate coefficients have been measured for relative energies from 0 up to 125 eV. For energies greater than about 20 meV the experimental result is well described by the theory for radiative recombination (RR). Below 20 meV the experimental rate increasingly exceeds the RR calculation. This so called "low-energy rate enhancement", observed previously in the recombination of light ions, has been investigated for the first time in the recombination of the heaviest ions. The rate enhancement is shown to scale as Z^2.6 for bare ions. The recombination rate enhancement is insensitive to changes of the electron density. Variation of the magnetic guiding field strength from 70 mT to 150 mT resulted in oscillations of the recombination rate at 0 eV. The oscillations are partly attributed to changes of the transverse electron temperature accompanying the change of the magnetic guiding field strength.