%0 Journal Article
%T Spectroscopy of $^{28}$Na: shell evolution toward the drip line
%A A. Lepailleur
%A K. Wimmer
%A A. Mutschler
%A O. Sorlin
%A V. Bader
%A C. Bancroft
%A D. Barofsky
%A B. Bastin
%A T. Baugher
%A D. Bazin
%A V. Bildstein
%A C. Borcea
%A R. Borcea
%A B. A. Brown
%A L. Caceres
%A A. Gade
%A L. Gaudefroy
%A S. Gr¨¦vy
%A G. F. Grinyer
%A H. Iwasaki
%A E. Khan
%A T. Kr£¿ll
%A C. Langer
%A A. Lemasson
%A O. Llidoo
%A J. Lloyd
%A F. Negoita
%A F. de Oliveira Santos
%A G. Perdikakis
%A F. Recchia
%A T. Redpath
%A T. Roger
%A F. Rotaru
%A S. Saenz
%A M. -G. Saint-Laurent
%A D. Smalley
%A D. Sohler
%A M. Stanoiu
%A S. R. Stroberg
%A J. C. Thomas
%A M. Vandebrouck
%A D. Weisshaar
%A A. Westerberg
%J Physics
%D 2015
%I arXiv
%R 10.1103/PhysRevC.92.054309
%X Excited states in $^{28}$Na have been studied using the $\beta$-decay of implanted $^{28}$Ne ions at GANIL/LISE as well as the in-beam $\gamma$-ray spectroscopy at the NSCL/S800 facility. New states of positive (J$^{\pi}$=3,4$^+$) and negative (J$^{\pi}$=1-5$^-$) parity are proposed. The former arise from the coupling between 0d$\_{5/2}$ protons and a 0d$\_{3/2}$ neutron, while the latter are due to couplings with 1p$\_{3/2}$ or 0f$\_{7/2}$ neutrons. While the relative energies between the J$^{\pi}$=1-4$^+$ states are well reproduced with the USDA interaction in the N=17 isotones, a progressive shift in the ground state binding energy (by about 500 keV) is observed between $^{26}$F and $^{30}$Al. This points to a possible change in the proton-neutron 0d$\_{5/2}$-0d$\_{3/2}$ effective interaction when moving from stability to the drip line. The presence of J$^{\pi}$=1-4$^-$ negative parity states around 1.5 MeV as well as of a candidate for a J$^{\pi}$=5$^-$ state around 2.5 MeV give further support to the collapse of the N=20 gap and to the inversion between the 0f$\_{7/2}$ and 1p$\_{3/2}$ levels below Z=12. These features are discussed in the framework of Shell Model and EDF calculations, leading to predicted negative parity states in the low energy spectra of the $^{26}$F and $^{25}$O nuclei.
%U http://arxiv.org/abs/1503.08568v1