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New Neutron Rich Nuclei Near {sup 208}Pb

By J. Aeystoe, A. Andreyev, A.-H. Evensen, P. Hoff, M. Huhta, M. Huyse, ISOLDE Collaboration, A. Jokinen, M. Karny, E. Kugler, J. Kurpeta, J. Lettry, A. Nieminen, A. Plochocki, M. Ramdhane, H. Ravn, K. Rykaczewski, J. Szerypo, P. VanDuppen, G. Walter and A. Woehr


The level properties near the stable doubly-magic nuclei formed the experimental grounds for the theoretical description of nuclear structure. However with a departure from the beta-stability line, the classical well-established shell structure might be modified. In particular, it may even vanish for extremely exotic neutron-rich nuclei near the neutron-drip line. Presently, it is impossible to verify such predictions by a direct experimental studies of these exotic objects. However, one may try to observe and understand the evolution of the nuclear structure while departing in the experiment as far as possible from the stable nuclei. An extension of experimental nuclear structure studies towards the nuclei characterized by high neutron excess is crucial for such verifications as well as for the {tau}-process nucleosynthesis scenario. Heavy neutron-rich nuclei, south-east of doubly-magic {sup 208}Pb, were always very difficult to produce and investigate. The nuclei like {sup 218}Po and {sup 214}Pb or {sup 210}Tl marked the border line of known nuclei from the beginning of the radioactivity era for over ninety years. To illustrate the difficulties, one can refer to the experiments employing the on-line mass separator technique. A spallation of heavy targets like {sup 232}Th and {sup 238}U by high-energy protons was proven as a source of heavy neutron-rich nuclei. The isotopes near and beyond doubly-magic {sup 208}Pb were produced too. However, such studies often suffered from an isobaric contamination of much more strongly produced and efficiently released elements like francium or radon and their decay products. A new experimental technique, based on the pulsed release element selective method recently developed at the PS Booster-ISOLDE at CERN [7,8,9] greatly reduces the contamination of these very short-lived {alpha}-emitters (Z {ge} 84) for the isobaric mass chains A=215 to A=218

Topics: Lead 208, Daughter Products, Neutrons, Nucleosynthesis, Mass, 73 Nuclear Physics And Radiation Physics, Nuclei, Nuclear Physics, Nuclear Structure
Publisher: Oak Ridge National Laboratory
Year: 1998
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Provided by: UNT Digital Library
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