First Evidence of Shape Coexistence in the Ni78 Region: Intruder 02+ State in Ge80

May 5, 2016
5 pages
Published in:
  • Phys.Rev.Lett. 116 (2016) 18, 182501
  • Published: May 5, 2016

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Abstract: (APS)
The N=48 Ge80 nucleus is studied by means of β-delayed electron-conversion spectroscopy at ALTO. The radioactive Ga80 beam is produced through the isotope separation on line photofission technique and collected on a movable tape for the measurement of γ and e- emission following β decay. An electric monopole E0 transition, which points to a 639(1) keV intruder 02+ state, is observed for the first time. This new state is lower than the 21+ level in Ge80, and provides evidence of shape coexistence close to one of the most neutron-rich doubly magic nuclei discovered so far, Ni78. This result is compared with theoretical estimates, helping to explain the role of monopole and quadrupole forces in the weakening of the N=50 gap at Z=32. The evolution of intruder 02+ states towards Ni78 is discussed.