First signs of collectivity in N = 86 and 88 isotones above ¹³²Sn

Abstract

Within the shell-model framework the low-lying states energies, E2 and M1 transitions of chains of nuclei 52 ≤ Z ≤ 60 with 82 ≤ N ≤ 88 are investigated. We use the N3LOP effective interaction derived from Effective Field Theory Potentials and phenomenologically constrained. We noticed clear collective features in N = 86 and 88 isotones, with signature of triaxial γ-bands.

First lifetime investigations of N>82 iodine isotopes: The quest for collectivity

“…As the previously known (5/2 + ) → (7/2 + ) ground state transitions in the 137,139 I isotopes are not observed in this work, their contribution is assumed to be negligible. The following relative yields are obtained: Y ( 137 I / 135 I) = 4.0(11) and Y ( 137 I / 139 I) = 1.5 (8). While the latter ratio compares well the estimated yields for A = 137 and 139, the 135 I nucleus seems to be produced about a factor of 2 less with a yield of about 0.9(2) %.…”

“…The study of nuclei with few valence particles outside the doubly magic 132 Sn core provides important information on two-body matrix elements to test realistic interactions employed in nuclear shell-model calculations. The development of collectivity outside the 132 Sn core is of current interest [1][2][3][4][5][6][7][8][9] and experimental findings provide a valuable input for state-of-the-art nuclear theories. The high degree of regularity in excitation energies along isotonic chains for nuclei "northeast" of 132 Sn project the overall behavior in that region.…”

Evolution of proton single-particle states in neutron-rich Sb isotopes beyond N=82

“…This reduction has been interpreted in Ref. [47] as being due to the coupling between single-particle states and collectivity. A similar behavior was also observed in a larger model space (π sdg, ν p f h) [48] and assessed on the basis of a spin-tensor decomposition [50].…”

“…Here, in the spirit of Zuker [43], the applied two-body monopole corrections mimic the effects of three-body forces, which are missing in the initial realistic interaction. In the past, the N3LOP effective interaction was shown to provide a very good overall description of the spectroscopic properties of a large number of nuclei in the quadrant northeast of 132 Sn, revealing the presence of large quadrupole collectivity in the N = 86, 88 isotones [44][45][46][47][48].…”

“…This feature was already discussed in Refs. [47][48][49]. In the first, the effective SPE were calculated, showing a decrease of the proton gap with increasing neutron number with the inversion taking place at N = 90.…”