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Shape coexistence in odd and odd-odd nuclei in the A = 100 region

Abstract : The region of neutron rich nuclei near A=100 is distinctive for the sudden change in the ground state properties of nuclei. In particular, for the even $_{38}$Sr and $_{40}$Zr isotopes a sudden onset of strong deformations at N=60 is observed, whereas the lighter isotopes up to N=58 are rather spherical. The isotones with N=59 neutrons are of special interest because they are just at the border between the two regions. Very recently, we have studied these odd-neutrons and odd-odd nuclei, by means of prompt-gamma spectroscopy of spontaneous fission of $^248}$Cm, using EUROGAM2 multidetector, and by measurements of microsecond isomers produced by fission of $^{241}$Pu at ILL reactor (Grenoble). In the latter case, the detection is based on time correlations between fission fragments selected by the LOHENGRIN mass spectrometer, and gamma-rays and conversion electrons from the isomers. It was found that in the odd nuclei of Sr and Zr three different shapes coexist. The ground state and low-lying levels are rather spherical, while deformed bands with $\beta_2$=0.3 are present at about 600 keV and the maximum deformation of the mass region, $\beta_2$=0.42 is reached for bands at about 1 MeV excitation energy. In the odd-odd nuclei, only two different shapes were found: the low-lying levels are rather spherical and deformed bands appear at about 500 keV. These new data allow to understand the origin of the deformation and the shape coexistence phenomenon observed in this mass region. The predominant role played by the unique-parity state $\nu g_{9/2}$ and $\nu h_{11/2}$ will be discussed.
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Submitted on : Tuesday, January 17, 2006 - 4:17:52 PM
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  • HAL Id : in2p3-00025424, version 1




J.A. Pinston. Shape coexistence in odd and odd-odd nuclei in the A = 100 region. 16th International School on Nuclear Physics, Neutron Physics, and Nuclear Energy, Sep 2005, Varna, Bulgaria. pp.48-54. ⟨in2p3-00025424⟩



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