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Séminaires généraux

A bubble nucleus to probe the spin-orbit force in extreme conditions

par Olivier Sorlin (Ganil)

Europe/Paris
Salle 101 (LAL)

Salle 101

LAL

Bât.200
Description
The spin orbit (SO) force plays a crucial role in nuclear structure to create most of the shell gaps and magic nuclei. It is essential as well to account for a possible island of stability in the superheavy nuclei (SHE) as well as to model explosive stellar nucleosynthesis (such as the rapid neutron capture process- the r-process) in which the main survivors are magic nuclei. The SO force has been postulated more than 60 years ago, and now theoretical descriptions in the framework of relativistic mean field model exist. However, models differ significantly towards the drip line for more than 40 years, where SHE may exhibit enhanced stability, and where the r-process occurs, owing to the fact that this force could never be tested in such unusual conditions in nuclear densities. We propose to study for the first time the unknown components (density and isospin dependence) of the SO force by using the doubly-magic bubble nucleus 34Si, in which a central proton density depletion is present. The one-proton (neutron) knockout reaction was used from a 34Si radioactive beam at the NSCL/MSU (USA) facility to determine its proton (neutron) density profile, based on the ‘measured' occupancies of the proton (neutron) orbits. The 33Al (33Si) residues were identified by the S800 spectrometer in coincidence with their gamma-rays detected in the Gretina array. In a second experiment the change of the neutron SO between a normal nucleus 36S and the bubble nucleus 34Si was determined by using the neutron adding (d,p) reaction at the GANIL facility in Caen. The protons were detected in the highly segmented MUST2 detector and the gamma-rays were detected in coincidence with the EXOGAM segmented Ge array. Consequences and perspectives related to this study of the SO interaction will be discussed.
Poster
Transparents