European Nuclear Physics Conference 2025

Study of proton and neutron contributions to the excitation of the 2+ states in Si isotopes between N=20 and N=28

Not scheduled

20m

Moho

Oral Presentation Nuclear Structure, Spectroscopy and Dynamics Parallel session

Speaker

Dr Stephane Grevy (LP2I Bordeaux)

Description

Studying the structure of exotic nuclei near shell closures is a powerful tool to investigate the underlying nuclear forces. The regions around N=20N=20 and N=28N=28 are known to exhibit significant shape transitions arising from a subtle interplay between monopole evolution—such as the tensor force—and quadrupole excitations leading to deformation.

Previous studies have shown that the deformation around 32Mg32Mg is primarily driven by neutron excitations across the N=20N=20 shell gap, whereas in the N=28N=28 region, deformation arises from both proton excitations within the sdsd shell and neutron excitations above N=28N=28. However, the relative contributions of protons and neutrons remain unclear, and spectroscopic data are still lacking to more tightly constrain theoretical models.

To address this, we conducted combined experiments at LISE aimed at measuring both the B(E2;0+→2+) transition probabilities and the inelastic proton scattering cross-sections for the 2+ states in silicon isotopes between N=20 and N=28. The experiment took place during the 2022 campaign at the LISE spectrometer, utilizing two independent and complementary experimental setups:

The first setup employed the active target ACTAR to measure inelastic scattering on a gaseous proton target. The second was dedicated to Coulomb excitation measurements using EXOGAM, PARIS, and the newly developed Zero Degree Detector (ZDD).

The collected data are currently under analysis. Preliminary results from both setups will be presented, along with new shell model calculations carried out by F. Nowacki and collaborators.