Etude des fermetures de couche N=40 et N=50

Abstract : On N=50, an experiment was done in February 2001 on the ISOL line PARRNe, the issue was to measure the first excited states of 83Ge (Z=32, N=51) by studying the beta decay of 83Ga produced by fission of 238U. The extreme precision of the experimental device, with the operation of hot plasma ion sources made it possible to reach spectroscopic information of the Ge isotopes beyond the magic gap N=50. Two transitions have been attributed to 83Ge: at 867 keV and at 1238 keV. The level scheme of 83Ge could be interpreted in terms of single particle: the excited states of this nucleus are due to the couplings between the single neutron beyond N=50 and the remaining nucleons. On N=40, we wanted to determine the transition probability between ground state and first excited state, called B(E2), in 70Ni (N=42) and 74Zn (N=44) from Coulomb excitation. These exotic nuclei are produced by fragmentation of a primary beam of 76Ge on a target of 58Ni, selected by the spectrometer LISE, then interact with a secondary Pb target to induce the Coulomb excitation. At the end of this analysis, the following values have been obtained: B(E2,70Ni)=860(170) e2fm4, B(E2,74Zn)=1960(140) e2fm4. These values have been compared on the one hand to variational calculations which I have realised, on the other hand to published shell model calculations. These calculations point out the complex aspect of the Ni nuclei, which do not seem to have a typical behaviour of semi magic nuclei although they are located on a closed shell in protons (Z=28),
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Nuclear Theory [nucl-th]. Université Paris Sud - Paris XI, 2004. French


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Submitted on : Wednesday, January 12, 2005 - 3:20:46 PM
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Orianna Perru. Etude des fermetures de couche N=40 et N=50. Nuclear Theory [nucl-th]. Université Paris Sud - Paris XI, 2004. French. <tel-00008024>

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