Seminar Details

Open questions related to shell evolution and nuclear forces: selected benchmarking experiments from GANIL

Olivier Sorlin, GANIL
Wednesday, September 12, 4:00 PM - Nuclear Science Seminar
NSCL Lecture Hall

Magic nuclei are cornerstones of nuclear structure. Due to the presence of large shell gaps between occupied and valence shells, they are spherical, have large excitation energies and weak excitation probabilities. They are often more abundant than other nuclei in the universe, play key roles in explosive nucleosynthesis, and could bind superheavy nuclei despite the large repulsive coulomb interaction. Our vision of immutable magic numbers, whatever the proton to neutron ratio, has been drastically changed these last years. In particular it has been demonstrated that the neutron magic numbers 8, 20 and 28 were vanishing far from stability. In parallel new magic numbers appear as N=16. These discoveries arose with the advent of radioactive ion beam facilities worldwide as well as progresses in detection systems. They pose fundamental questions such as: which parts of the nuclear force drive these modifications of shell closures? Are such effects observed throughout the chart of nuclides, or are they limited to medium mass nuclei? To which extent nuclear forces are changing when approaching the drip line ? What are the consequences of these shell modifications for explosive nucleosynthesis, and for the existence of superheavy nuclei? The present talk will present recent experimental studies performed at GANIL using transfer (d,p) reactions, and the combination of beta-decay and isomeric studies. The obtained results on the 69Ni, 34,35Si and 26F nuclei aim at addressing three important aspects of the nuclear force such as the three body force, the spin-orbit interaction and the behavior of nuclear forces at drip line, respectively. Tentative results and interpretations will be proposed.