Local suppression of collectivity in theN=80isotones at theZ=58subshell closure

Abstract

Background: Recent data on N = 80 isotones have suggested that the proton π (1g 7/2 ) subshell closure at Z = 58 has an impact on the properties of low-lying collective states. Purpose: Knowledge of the B(E2; 2 + 1 → 0 + 1 ) value of 140 Nd is needed in order to test this conjecture. Method: The unstable, neutron-rich nucleus 140 Nd was investigated via projectile Coulomb excitation at the REX-ISOLDE facility with the MINIBALL spectrometer. Results: The B(E2) value of 33(2) W.u. expands the N = 80 systematics beyond the Z = 58 subshell closure. Conclusions:The measurement demonstrates that the reduced collectivity of 138 Ce is a local effect possibly due to the Z = 58 subshell closure and requests refined theoretical calculations. The latter predict a smoothly increasing trend.

Nuclear-structure studies of exotic nuclei with MINIBALL

“…Bauer et al [44] and Stegmann et al [45] Nd has the expected dependence on p n N N (whereas a dip is observed [92] for 58 138 Ce corresponding to the p ( ) g 7 2 subshell closure at Z=58), the value for 62 142 Sm deviates significantly from the p n N N behavior, reflecting the impact of the p ( ) g d 1 2…”

“…Bauer et al [44] and Stegmann et al [45] investigated the evolution of quadrupole collectivity for the N=80 isotones, by measuring the  Rn. They observed that contributions from collective excitations are present in these nuclei when moving away from the N=126 closed shell, although they have been proposed to lie in, or at the boundary of the region where the seniority scheme should persist.…”

“…The extended REX-ISOLDE acceleration scheme was readily applied to even heavier ions and enabled detailed studies of shapes and collectivity in very neutron-rich and neutrondeficient Se, Kr, Rb and Sr nuclei [37][38][39][40][41][42] as well in the rare-earth region [43][44][45]. In recent years results for neutron-deficient Hg, Pb, Po, Rn isotopes were also obtained from CE experiments which provided valuable and complementary insights to the understanding of the structure of this mass region to that obtained using heavy-ion induced fusion reactions [46][47][48].…”