CERN Accelerating science

Article
Title	Identification of the crossing point at $N=21$ between normal and intruder configurations
Author(s)	Lică, R (CERN ; Bucharest, IFIN-HH) ; Rotaru, F (Bucharest, IFIN-HH) ; Borge, M J G (CERN ; Madrid, Inst. Estructura Materia) ; Grévy, S (GANIL ; CENBG, Gradignan) ; Negoiţă, F (Bucharest, IFIN-HH) ; Poves, A (Madrid, Autonoma U.) ; Sorlin, O (GANIL) ; Andreyev, A N (York U., England) ; Borcea, R (Bucharest, IFIN-HH) ; Costache, C (Bucharest, IFIN-HH) ; De Witte, H (KU Leuven, Dept. Phys. Astron.) ; Fraile, L M (UCM, Madrid, Dept. Phys.) ; Greenlees, P T (Jyvaskyla U. ; Helsinki U.) ; Huyse, M (KU Leuven, Dept. Phys. Astron.) ; Ionescu, A (Bucharest, IFIN-HH) ; Kisyov, S (Bucharest, IFIN-HH) ; Konki, J (Jyvaskyla U. ; Helsinki Inst. of Phys.) ; Lazarus, I (Daresbury) ; Madurga, M (CERN) ; Mărginean, N (Bucharest, IFIN-HH) ; Mărginean, R (Bucharest, IFIN-HH) ; Mihai, C (Bucharest, IFIN-HH) ; Mihai, R E (Bucharest, IFIN-HH) ; Negret, A (Bucharest, IFIN-HH) ; Page, R D (Liverpool U.) ; Pakarinen, J (Jyvaskyla U. ; Helsinki Inst. of Phys.) ; Pascu, S (Bucharest, IFIN-HH) ; Pucknell, V (Daresbury) ; Rahkila, P (Jyvaskyla U. ; Helsinki Inst. of Phys.) ; Rapisarda, E (CERN) ; Şerban, A (Bucharest, IFIN-HH) ; Sotty, C O (Bucharest, IFIN-HH) ; Stan, L (Bucharest, IFIN-HH) ; Stănoiu, M (Bucharest, IFIN-HH) ; Tengblad, O (Madrid, Inst. Estructura Materia) ; Turturică, A (Bucharest, IFIN-HH) ; Van Duppen, P (KU Leuven, Dept. Phys. Astron.) ; Wadsworth, R (York U., England) ; Warr, N (Cologne U.)
Collaboration	IDS
Publication	2017
Number of pages	6
In:	Phys. Rev. C 95 (2017) 021301
DOI	10.1103/PhysRevC.95.021301
Subject category	Nuclear Physics - Experiment
Accelerator/Facility, Experiment	CERN ISOLDE
Abstract	The β− decay of Mg34 was used to study the Al34 nucleus through γ spectroscopy at the Isotope Separator On-Line facility of CERN. Previous studies identified two β-decaying states in Al34 having spin-parity assignments Jπ=4− dominated by the normal configuration π(d5/2)−1⊗ν(f7/2) and Jπ=1+ by the intruder configuration π(d5/2)−1⊗ν(d3/2)−1(f7/2)2. Their unknown ordering and relative energy have been the subject of debate for the placement of Al34 inside or outside the N=20 “island of inversion.” We report here that the 1+ intruder lies only 46.6 keV above the 4− ground state. In addition, a new half-life of T1/2=44.9(4)ms, that is twice as long as the previously measured 20(10) ms, has been determined for Mg34. Large-scale shell-model calculations with the recently developed sdpf-u-mix interaction are compared with the new data and used to interpret the mechanisms at play at the very border of the N=20 island of inversion.
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