pre-PAC Workshop for AGATA@LNL

Towards the 132Sn nucleus via lifetime measurements

6 Oct 2022, 15:00

25m

INFN-LNL

Session: LoI 4

Speaker

Dr Marco Siciliano (Argonne National Laboratory)

Description

Properties of low-lying states in Z≈50 nuclei have been in the focus of both experimental and theoretical communities to systematically investigate the evolution of nuclear features, from neutron-deficient to neutron-rich cases.
While in the neutron-rich Sn and Te nuclei the excitation energy of the $2^+_1$ and $4^+_1$ levels and the B(E2;$2^+_1 \to 0^+_{g.s.}$) values have traditionally been described in the context of the generalized seniority scheme, several experimental results put in doubt this interpretation. The generalized-seniority interpretation is also challenged by large-scale shell-model theoretical calculations, which predict a completely different trend of the B(E2;$4^+_1 \to 2^+_1$) values.
Furthermore, due to the proximity to Z=50 and N=82 shell closures, the structure of both Te and Sn isotopes presents peculiar features that make these nuclei the perfect test bench to investigate the single-particle excitations of both protons and neutrons, and also their coupling in the nuclear Hamiltonian. Unfortunately, precise experimental information, which could shed light on the structure of nuclei in this mass region, is missing.

For these reasons, we propose a direct measurement of the lifetimes of low-lying excited states in $^{126,128,130}$Sn and $^{128,130,132}$Te aiming for an uncertainty around $10\%$. Additionally, the lifetime of other low-lying states will be measured in $^{130}$Te, providing crucial complementary information for the neutrino-less double $\beta$-decay investigation performed by the collaboration via Coulomb-excitation measurement.
In order to achieve these goals, we propose a multi-nucleon transfer reaction of a $^{197}$Au beam at 1122 MeV on a $^{130}$Te target: the reaction products and the emitted $\gamma$ rays will be detected by PRISMA and AGATA spectrometers, respectively, while the dedicated plunger will be used for the lifetime measurements.