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Abstract |
Low-lying states of Zr-94 were investigated via low-energy multi-step Coulomb excitation. From the measured gamma-ray yields, 16 reduced E2 transition probabilities between low-spin states were determined, together with the spectroscopic quadrupole moments of the 2(1,2)+ states. Based on this information, for the first time in the Zr isotopic chain, the shapes of the 0(1,2)(+) states including their deformation softness were inferred in a model-independent way using the quadrupole sum rules approach. The ground state of Zr-94 possesses a rather diffuse shape associated with a spherical configuration, while the 0(2)(+) state is triaxial tending towards oblate and more strongly deformed. The observed features of shape coexistence in Zr-94 are consistent with both Monte-Carlo shell-model predictions and IBM-CM calculations, and provide model-independent constraints on the shape character assigned in the IBM-CM to the intruder configuration in Zr92-96. |
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