Extension of the N=40 Island of Inversion towards N=50: Spectroscopy of 66Cr, 70,72Fe

C. Santamaria (1) , A. Obertelli (1) , D. Calvet (2) , F. Chateau (2) , A. Corsi (1) , A. Delbart (2) , J.M. Gheller (3) , A. Gillibert (1) , V. Lapoux (1) , C. Peron (4) , A. Peyaud (2) , E. Pollacco (1) , J.Y. Rousseau (4)

1 DPHN - Département de Physique Nucléaire (ex SPhN)
2 DEDIP - Département d'Electronique, des Détecteurs et d'Informatique pour la Physique (ex SEDI)
3 DACM - Département des Accélérateurs, de Cryogénie et de Magnétisme (ex SACM)
4 DIS - Département d'Ingénierie des Systèmes (ex SIS)

We report on the measurement of the rst 2+ and 4+ states of 66Cr and 70;72Fe via in-beam -ray spectroscopy. The nuclei of interest were produced by (p; 2p) reactions at incident energies of 260 MeV/nucleon. The experiment was performed at the Radioactive Isotope Beam Factory, RIKEN using the DALI2 -ray detector array and the novel MINOS device, a thick liquid hydrogen target combined with a vertex tracker. A low-energy plateau of 2+ 1 and 4+ 1 energies as a function of neutron number was observed for N38 and N40 for even-even Cr and Fe isotopes, respectively. State-of-the-art shell model calculations with a modied LNPS interaction in the pfg9=2d5=2 valence space reproduce the observations. Interpretation within the shell model shows an extension of the Island of Inversion at N=40 towards neutron-rich isotopes and hints at a smooth transition to collective N=50 Cr and Fe isotopes.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

C. Santamaria, A. Obertelli, D. Calvet, F. Chateau, A. Corsi, et al.. Extension of the N=40 Island of Inversion towards N=50: Spectroscopy of 66Cr, 70,72Fe. 2015. ⟨hal-01156540⟩