Shape coexistence in odd and odd-odd nuclei in the A $sim$ 100 regionReport as inadecuate

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1 LPSC - Laboratoire de Physique Subatomique et de Cosmologie 2 ILL - Institut Laue-Langevin

Abstract : In the even-even nuclei around A=100 a transition from spherical to deformed shapes occurs from N=58 to N=60. The isotones with N=59 are of special interest, because they are just at the border between the two regions. Very recently, we have studied odd-neutrons and odd-odd nuclei with N=59, by means of prompt $\gamma$-ray spectroscopy of the spontaneous fission of $^{247}$Cm, using the EUROGAM 2 multi-detector, and by measurements of $\mu$s isomers produced by fission of $^{239,241}$Pu with thermal neutrons at ILL Grenoble. In the latter case, the detection is based on time correlation measurements between fission fragments detected by the LOHENGRIN mass spectrometer and $\gamma$-rays or conversion electrons from the isomer decay. It was found that three shapes coexist in the odd $^{97}$Sr and $^{99}$Zr and two shapes coexist in the odd-odd $^{96}$Rb. A simple explanation of the shape-coexistence mechanism is proposed. It is based upon the Nilsson diagram and stresses the fundamental importance of the unique parity states.

Keywords : exotic nuclei shape coexistence nuclei with mass number 90 to 149 nuclear shape deformed nuclei nuclear energy level transitions spontaneous fission neutron-nucleus reactions fission of plutonium

Author: J.A. Pinston - J. Genevey - G.S. Simpson - W. Urban



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