New region of maximum octupole collectivity in the rare-earth nuclei: The case of Gd isotopes

Résumé fourni par la source

We present the first evidence of maximum octupole collectivity in the Gd isotopic chain through a direct measurement of an enhanced B(E3) value in 150Gd. This result was achieved via two highly sensitive experiments designed to determine the lifetime of the first 3− state and the weak E3 decay branch to the ground state. With a measured E3 strength of 45(5) W.u., this value ranks among the highest and most precise recorded in this region, comparable in strength to those observed in neutron-rich Ba nuclei, a region traditionally known for its enhanced octupole collectivity. We compare the available experimental results for the E3 strengths in the Gd isotopic chain with five state-of-the-art theoretical models: the quasi-particle random phase approximation, the time-dependent Hartree-Fock, the quadrupole-octupole collective Hamiltonian, the meanfield mapped interacting boson model, and the triaxial projected shell model. We conclude that QRPA provides a strong explanation for the increasing trend of B(E3) values in Gd nuclei with N=82–86.

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