2020 Impact factor 3.043
Hadrons and Nuclei
Eur. Phys. J. A 2, 179-191

Fission of highly excited fragments from collisions of 750 A.MeV $^{\bf 238}$U-ions on $^{\bf 208}$Pb

W. Schwab1,2 - M. Bernas2 - P. Armbruster1 - S. Czajkowski1,3 - Ph. Dessagne4 - C. Donzaud1,2 - H. Geissel1 - A. Heinz1,6 - C. Kozhuharov1 - C. Miehé4 - G. Münzenberg1 - M. Pfützner1,5 - C. Stéphan2 - K. Sümmerer1 - L. Tassan-Got2 - B. Voss1,6

1 Gesellschaft für Schwerionenforschung, Planckstr. 1, D-64291 Darmstadt, Germany
2 Institut de physique nucléaire d'Orsay, IN2P3-CNRS, BP 1, F-91400 Orsay, France
3 Centre d'Etude Nucléaire de Bordeaux-Gradignan, IN2P3-CNRS, BP 120, F-33175 Gradignan, France
4 Institut de Recherches Subatomiques, IN2P3-CNRS BP 28, F-67037 Strasbourg, France
5 Instytut Fizyki Doswiadczalnej, Uniwersytet Warszawski, Hoza 69, PL-00681 Warszawa, Poland
6 Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstr. 9, D-64289 Darmstadt, Germany

Received: 26 January 1998 / Revised version: 16 March 1998 Communicated by V. Metag

Abstract
Fragments of relativistic 750 A.MeV U-projectiles were investigated by using the fragment separator FRS for magnetic selection of reaction products including ray-tracing and $\Delta$E-ToF techniques. For elements between Ge and Sb, measurements of isotopic yield distributions and velocities revealed three processes: fragmentation, low-energy fission, and high-energy fission. The last of these regimes is presently reported. First and second moments of distributions of mass numbers, atomic numbers and velocities of the corresponding fragments allowed us to identify 10143Tc56 as the most probable fragment of a high energy symmetric fission reaction. Moreover, we could deduce a hypothetical mean fissioning fragmentation product 208Rn and its highly excited pre-fragmentation parent 227Ra produced in a primary abrasion reaction at an excitation energy of about 290 MeV.

PACS
25.85.-w Fission reactions - 25.75.-q Relativistic heavy-ion collosions


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