Rapid onset of collectivity in the vicinity of 78Ni

Lebois Matthieu; David Verney; Fadi Ibrahim; Said Essabaa; Faiçal Azaiez; Maher Cheikh Mhamed; Evelyne Cottereau; Cuong Phan Viet; Mathieu Ferraton; Kieran Flanagan; Serge Franchoo; Dominique Guillemaud Mueller; Fairouz Hammache; Christophe Lau; François Le Blanc; Jean François Le Du; Baptiste Mouginot; Costel Petrache; Brigitte Roussière; Lionel Sagui; Nicolas De Sereville; Iulian Stefan; Benoit Tastet

arXiv · 0810.3890

Rapid onset of collectivity in the vicinity of 78Ni

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Abstract

gamma-rays following the B and B-n decay of the very neutron rich 84Ga produced by photo-fission of 238U have been studied at the newly built ISOL facility of IPN Orsay: ALTO. Two activities were observed and assigned to two B-decaying states: 84gGa, I = (0\^-) and 84mGa, I = (3\^-, 4\^-). Excitation energies of the 2+1 and 4+1 excited states of 84Ge were measured at E(2+1) = 624.3 keV and E(4+1) = 1670.1 keV. Comparison with HFB+GCM calculations allows to establish the collective character of this nucleus indicating a substantial N=50 core polarization. The excitation energy of the 1/2+1 state in 83Ga known to carry a large part of the neutron 3s1/2 strength was measured at 247.8keV. Altogether these data allow to confirm the new single particle state ordering which appears immediately after the double Z=28 and N=50 shell closure and to designate 78Ni as a fragile and easily polarized doubly-magic core.

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Lebois Matthieu, David Verney, Fadi Ibrahim, Said Essabaa, Faiçal Azaiez, Maher Cheikh Mhamed, Evelyne Cottereau, Cuong Phan Viet, Mathieu Ferraton, Kieran Flanagan, Serge Franchoo, Dominique Guillemaud Mueller, Fairouz Hammache, Christophe Lau, François Le Blanc, Jean François Le Du, Baptiste Mouginot, Costel Petrache, Brigitte Roussière, Lionel Sagui, Nicolas De Sereville, Iulian Stefan, Benoit Tastet. 2008-10-21. Rapid onset of collectivity in the vicinity of 78Ni. https://arxiv.org/abs/0810.3890

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