Low-energy fission investigated in reactions of 750 AMeV
U-ions on 
Pb. II: Isotopic distributions
C. Donzaud1,2 - S. Czajkowski2,3 - P. Armbruster2 - M. Bernas1 - C. Böckstiegel5 - Ph. Dessagne4 - H. Geissel2 - E. Hanelt5 - A. Heinz5 - C. Kozhuharov2 - Ch. Miehé4 - G. Münzenberg2 - M. Pfützner6 - W. Schwab2 - C. Stéphan1 - K. Sümmerer2 - L. Tassan-Got1 - B. Voss2,5
1 IPN Orsay, IN2P3, CNRS, F-91406 Orsay Cedex, France
2 GSI Darmstadt, HGF, Postfach 110552, D-64220 Darmstadt, Germany
3 CENBG Bordeaux-Gradignan, IN2P3, CNRS, BP 120, F-33170 Gradignan Cedex, France
4 IReS Strasbourg, IN2P3, CNRS, F-67037 Strasbourg Cedex, France
5 TH Darmstadt, Institut für Kernphysik, Schlossgartenstrasse 9, D-64289
Darmstadt, Germany
6 IFD, University Warsaw, Pl-00681 Warsaw, Hoza 69, Poland
Received: 14 July 1997 / Revised version: 6 October 1997 Communicated by V. Metag
Abstract
Projectile fission of 750 AMeV 238U-ions interacting with a Pb
target was studied by means of the spectrometer FRS, GSI-Darmstadt. One of the
two fission fragments was detected with a transmission of few percent and
identified in mass and charge. Low-energy fission (E*<25 MeV) events were
selected by their magnetic rigidity. Whereas the production of asymmetric fission
events is dominated by the GDR excitation, very asymmetric fission and symmetric
fission take place after a GQR or DGDR excitation or after a nuclear interaction.
Cross sections of more than 250 isotopes were measured. Isotopic distributions of
low-energy fission were reconstructed for elements from Se to Te. The fission
modes SI, SII and SL were clearly shown in these distributions and in the mass
and TKE distributions. Charge polarization and mass dispersion were deduced for
each fission mode. Finally, the characteristics of the low-energy fission process
explain the production rates of neutron-rich species.
PACS
25.85.-W Fission reactions
Copyright Springer-Verlag
