Production cross-sections of neutron-rich Pb and Bi isotopes in the fragmentation of 238U
ABSTRACT Neutron-rich lead and bismuth isotopes have been produced by cold-fragmentation reactions induced by 238U projectiles at 1A GeV impinging on a beryllium target. The high-resolving power FRagment Separator (FRS) at GSI allowed
us to identify and determine the production cross-sections of 43 nuclei, nine of them for the first time ( 216, 217, 218, 219Pb and 219, 220, 221, 222, 223Bi . These data are compared to other previously measured cross-sections in similar reactions and model calculations.
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ABSTRACT: 238U projectile fragments have been created at the entrance of the fragment separator FRS, spatially separated in flight within 0.45 μs and injected into the storage-cooler ring ESR at 7.9 Tm corresponding to about 70% light velocity. Accurate new mass values and lifetime information of the stored exotic nuclei in the element range from platinum to uranium have been obtained with single-particle Schottky spectrometry. In this experiment the new isotopes of 236Ac, 224At, 221Po, 222Po, and 213Tl were discovered. The isotopes were unambiguously identified and their masses measured. In addition, the time-correlated data have provided information on the lifetime of the new nuclides. The discovery of isotopes along with accurate mass measurement has been achieved for the first time at the FRS-ESR facility. The results will contribute to the knowledge of the decay products from the r-process nuclei and enable a crucial test of the predictive power of modern nuclear mass and half-life models.Physics Letters B 03/2010; 691:234-237. DOI:10.1016/j.physletb.2010.05.078 · 6.02 Impact Factor
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ABSTRACT: The existence of nuclei with exotic combinations of protons and neutrons provides fundamental information on the forces acting between nucleons. The maximum number of neutrons a given number of protons can bind, neutron drip line1, is only known for the lightest chemical elements, up to oxygen. For heavier elements, the larger its atomic number, the farther from this limit is the most neutron-rich known isotope. The properties of heavy neutron-rich nuclei also have a direct impact on understanding the observed abundances of chemical elements heavier than iron in our Universe. Above half of the abundances of these elements are thought to be produced in rapid-neutron capture reactions, r-process, taking place in violent stellar scenarios2 where heavy neutron-rich nuclei, far beyond the ones known up today, are produced. Here we present a major step forward in the production of heavy neutron-rich nuclei: the discovery of 73 new neutron-rich isotopes of chemical elements between tantalum (Z=72) and actinium (Z=89). This result proves that cold-fragmentation reactions3 at relativistic energies are governed by large fluctuations in isospin and energy dissipation making possible the massive production of heavy neutron-rich nuclei, paving then the way for the full understanding of the origin of the heavier elements in our Universe. It is expected that further studies providing ground and structural properties of the nuclei presented here will reveal further details on the nuclear shell evolution along Z=82 and N=126, but also on the understanding of the stellar nucleosyntheis r-process around the waiting point at A~190 defining the speed of the matter flow towards heavier fissioning nuclei.
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ABSTRACT: The production of heavy neutron-rich nuclei has been investigated using cold-fragmentation reactions of U238 projectiles at relativistic energies. The experiment performed at the high-resolving-power magnetic spectrometer Fragment Separator at GSI made it possible to identify 40 new heavy neutron-rich nuclei: Pt205, Au207-210, Hg211-216, Tl214-217, Pb215-220, Bi219-224, Po223-227, At225-229, Rn230,231, and Fr233. The production cross sections of these nuclei were also determined and used to benchmark reaction codes that predict the production of nuclei far from stability.Physical Review C 10/2010; 82(4). DOI:10.1103/PhysRevC.82.041602 · 3.88 Impact Factor