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arXiv · 2508.05268

Quadrupole-hexadecapole coupling in the rare earth region with beyond mean field correlations

R. Rodriguez-Guzman·L. M. Robledo
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Abstract

The roles of static hexadecapole deformation and beyond-mean-field quadrupole-hexadecapole configuration mixing are studied for a selected set of Yb, Hf, W and Os isotopes within the mass range $170 \le A \le 202$, using the Hartree-Fock-Bogoliubov (HFB) and the two-dimensional Generator Coordinate Method (2D-GCM) approaches, based on the Gogny energy density functional. The 2D-GCM ground and excited states of the lighter isotopes are associated with diamond-like shapes while, for each isotopic chain, a region where those states correspond to square-like shapes has been found below the neutron shell closure $N=126$. It is shown, that for the studied nuclei the quadrupole and hexadecapole degrees of freedom are interwoven in the ground and excited states up to the mass number $A=184-188$. This structural evolution, encoded in the 2D-GCM collective wave functions, is accompanied by an enhanced prolate-oblate shape coexistence around the neutron number $N=116$. In agreement with previous studies, it is also shown that for the considered Yb, Hf, W and Os isotopes the inclusion of hexadecapole deformation in the ground state dynamics leads to a non trivial additional correlation energy comparable to the quadrupole correlation energy itself.

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R. Rodriguez-Guzman, L. M. Robledo. 2025-08-07. Quadrupole-hexadecapole coupling in the rare earth region with beyond mean field correlations. https://doi.org/10.1140/epja%2Fs10050-025-01638-x

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