CNRS Université Bordeaux

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Evolution of the N = 28, N = 50 and N = 82 Magic Numbers

Lucia Caceres, GANIL Caen
Vendredi 19 février 2010 à 10h30 Salle des Séminaires

It has been in the 50th when the experimental sequence of ``magic numbers’’ (8, 20, 50, 82 and 126), valid in the valley of stability, could be explained by adding a strong spin-orbit interaction to the mean field potential. Nowadays, with the development of the new radioactive beam facilities, we know that these numbers may change or even disappear when approaching the limits of the nuclear chart.

In this seminar, selected experimental results from GSI and GANIL which shed light to the evolution of the shell closures in nuclei with extreme N/Z ratio will be presented making reference to how the high intensity beams provided SPIRAL 2 facility will allow to puzzle out some of the challenges presented up to date. In the very neutron rich side of the nuclear chart, we will discuss the N = 82 shell closure through the isomeric decay of 130Cd and 131In nuclei located below 132Sn and its consequences for the r-process solar abundance calculation. Following, in the N = 28 isotones we will examin by means of the in-flight gamma-spectroscopy in 44S the influence of the N = 28 shell quenching to the appearance of deformation in the ``semi-magic’’ nuclei south 48Ca. And finally, we will come back shortly to the Sn isotopic chain but this time close to the self-conjugate 100Sn to try to understand the magicity character of this nucleus and how a possible reduction of N = 50 shell gap may cause the development of quadrupole excitations.