Deformation and mixing of coexisting shapes in neutron-deficient polonium isotopes

Abstract : Coulomb-excitation experiments are performed with postaccelerated beams of neutron-deficient $^{196,198,200,202}$Po isotopes at the REX-ISOLDE facility. A set of matrix elements, coupling the low-lying states in these isotopes, is extracted. In the two heaviest isotopes, $^{200,202}$Po, the transitional and diagonal matrix elements of the $2^+ _1$ state are determined. In $^{196,198}$Po multistep Coulomb excitation is observed, populating the $4^+_1$ , $0^+ _2$ , and $2^+_2$ states. The experimental results are compared to the results from the measurement of mean-square charge radii in polonium isotopes, confirming the onset of deformation from $^{196}$Po onwards. Three model descriptions are used to compare to the data. Calculations with the beyond-mean-field model, the interacting boson model, and the general Bohr Hamiltonian model show partial agreement with the experimental data. Finally, calculations with a phenomenological two-level mixing model hint at the mixing of a spherical structure with a weakly deformed rotational structure.
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Submitted on : Thursday, November 5, 2015 - 11:03:28 PM
Last modification on : Thursday, February 7, 2019 - 2:55:11 PM

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N. Kesteloot, B. Bastin, L. P. Gaffney, K. Wrzosek-Lipska, K. Auranen, et al.. Deformation and mixing of coexisting shapes in neutron-deficient polonium isotopes. Physical Review C, American Physical Society, 2015, 92 (5), pp.054301. ⟨10.1103/PhysRevC.92.054301⟩. ⟨in2p3-01225279⟩

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