Lifetimes and shape-coexisting states of $^{99}Zr$

Abstract : Lifetimes of intermediate-spin states in two rotational bands of $^{99}Zr$ have been measured. These states were populated following the neutron-induced fission of $^{235}U$ at the PF1B beamline of the Institut Laue-Langevin, Grenoble, during the EXILL-FATIMA campaign. The nucleus $^{99}Zr_{59}$ exhibits shape coexistence and lies precisely on the border of an abrupt change in ground-state deformation when going from N=58 to N=60, making its study interesting for understanding the mechanisms involved in the rapid onset of deformation here. The B(E2) values extracted for decays in the ν3/2[541] band allow quadrupole deformations of $\beta_2$=0.34(1) and 0.26(3) to be determined for the 821.6- and 1236.6-keV members, whereas $\beta_2$=0.32(3) was found for the 850.5-keV member of the ν3/2[411] band. Some of the excited states known in $^{99}Zr$ have been reasonably described with interacting boson-fermion model (IBFM) calculations. Type-II shell evolution is proposed to play a major role in modifying single-particle energies in $^{99}Zr$.
Keywords : Nuclear Structure
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Submitted on : Wednesday, August 14, 2019 - 9:41:43 AM
Last modification on : Friday, August 16, 2019 - 1:09:26 AM

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P. Spagnoletti, G. Simpson, S. Kisyov, D. Bucurescu, J.M. Régis, et al.. Lifetimes and shape-coexisting states of $^{99}Zr$. Phys.Rev.C, 2019, 100 (1), pp.014311. ⟨10.1103/PhysRevC.100.014311⟩. ⟨hal-02266377⟩



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