New nuclear structure data beyond 136Sn

R Lozeva

doi:10.1051/epjconf/201817802020

Abstract

Exotic nuclei beyond the 132Sn double shell-closure are influenced by both the Sn superfluity and the evolving collectivity only few nucleons away. Toward even more neutron-rich nuclei, especially at intermediate mass number, the interplay between single-particle and collective particle-hole excitations competes. In some cases with the extreme addition of neutrons also other effects as the formation of neutron skin, stabilization as sub-shell gaps or orbital crossings may be expected. The knowledge of nuclear ingredients is especially interesting beyond 132Sn and little is known on how the excitation modes develop with the addition of both protons and neutrons and for example systematic prompt and decay studies can be such very sensitive probe. Recently, we have approached this region of nuclei in several experimental measurements following 238U projectile fission on 9Be and n-induced fission on 241Pu and 235U. Consistent data analysis allows to access various spins and excitation energies and provide new input to theory. Examples from these studies on several nuclei in the A~140 region were presented during the conference together with the possible interpretation of the new data. Here, we will illustrate one example on 136I using two complementary data sets.

Highlights

Introduction and MotivationNuclei beyond 132Sn present very particular properties
Except the strong decay from the first 1+ state by the 2077.9 keV γ-ray, it is interesting to underline the detection of a 2656.0 keV transition, expected [13], but unobserved as a direct decay from this first 1+ state to the 1- g.s. state
One can neglect the different type of population between them for these levels, which will be discussed elsewhere together other new spectroscopy data on 136I [21]

Summary

Introduction and Motivation

Nuclei beyond 132Sn present very particular properties On one hand they are exotic, being far from stability, on the other - simple, as they are located close to the doubly-magic spherical nucleus 132Sn. generally single-valence particle excitations of few neutrons as in 135Sb, 136Sb [1,2] up to few protons away as in 135I, 136I [3,4] present rather simple descriptions. Differences exist in the predictions for N=90 sub-shell gap between the νf7/2 and νp3/2 orbitals [14], an assumption inconsistent with [15] Having worked in this region in several works to date, we provide indispensable ingredients to understand many of the open questions. It is important to further investigate the species close to N=82, to compare them with and explore the entire proton-neutron particle valence space beyond

Measuremens and Data

Discussion