Spectroscopy of 39,41Si and the border of the N = 28 island of inversion

D. Sohler , S. Grévy (1) , Zs. Dombrádi , O. Sorlin (2) , L. Gaudefroy (3) , B. Bastin (2) , N.L. Achouri (4) , J.C. Angélique (4) , F. Azaiez (5) , D. Baiborodin , R. Borcea , C. Bourgeois (5) , A. Buta , A. Burger , L. Caceres (2) , R. Chapman , J.C. Dalouzy (2) , Z. Dlouhy , A. Drouard (6) , Z. Elekes , S. Franchoo (5) , S. Iacob , I. Kuti , B. Laurent (4) , M. Lazar , X. Liang , E. Liénard (4) , S.M. Lukyanov , J. Mrazek , L. Nalpas (6) , F. Negoita , F. Nowacki (7) , N.A. Orr (4) , Yu.E. Penionzkhevitch , Zs. Podolyák , F. Pougheon (5) , A. Poves , P. Roussel-Chomaz (2) , M. Stanoiu , I. Stefan (5) , M.G. Saint-Laurent (2)

1 NEX - Noyaux exotiques
2 GANIL - Grand Accélérateur National d'Ions Lourds
3 DAM/DIF - DAM Île-de-France
4 LPCC - Laboratoire de physique corpusculaire de Caen
5 IPNO - Institut de Physique Nucléaire d'Orsay
6 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
7 IPHC - Institut Pluridisciplinaire Hubert Curien

The structure of the very neutron-rich nuclei 39Si and 41Si has been investigated via in-beam γ -ray spectroscopy and few-nucleon knockout from radioactive beams. The observation of low-lying states in 39Si is a clear evidence for a drastic lowering of the intruder neutron 3/2− state when going from Z = 20 to Z = 14. The energy of the only γ -ray transition (672(14) keV) observed in 41Si is significantly lower than that of the first excited state in 47Ca (2014 keV) suggesting a deformed ground state for 41Si. These results are consistent with large-scale shell-model calculations implying that strong proton- neutron correlations are the main reason for the lowering of the intruder configurations over the normal ones.

Mots clés: Nuclear structure; Knockout reactions; Shell closures; Neutron-rich Si nuclei

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

D. Sohler, S. Grévy, Zs. Dombrádi, O. Sorlin, L. Gaudefroy, et al.. Spectroscopy of 39,41Si and the border of the N = 28 island of inversion. Physics Letters B, 2011, 703, pp.417-421. ⟨10.1016/j.physletb.2011.08.004⟩. ⟨in2p3-00619310⟩