Speaker
Description
Experimental data on single-particle energies in weakly bound systems have materialized over the past decade or so. Perhaps the most discussed has been for the neutron-rich nuclei around $N = 20$ and 28. A smooth decrease in the separation of the $2p_{3/2}$-$2p_{1/2}$ spin-orbit splittings is observed in this region as they approach zero binding. This is at odds with the well-established trends of experimentally determined spin-orbit splittings across the chart of nuclides for well-bound states, as presented by Mairle [Phys. Lett. B 304, 39 (1993)]. In studying the contrast between experimental data, mean-field descriptions, and the trends discussed by Mairle for both well-bound and weakly bound systems across the nuclear chart, with a focus on neutron spin-orbit partners, a seemingly universal behavior emerges that could prove predictive. This can be tracked to unbound resonances in a systematic way. Many of the regions explored have connections to other prominent topics in nuclear physics, such as $r$-process nucleosynthesis, where the ordering of single-particle energies near threshold in weakly bound systems influences reaction rates. Throughout, I will highlight one of the principal techniques for extracting such data: the solenoidal spectrometer technique, now used at ATLAS, CERN, and FRIB.
| Contribution category | Experiment |
|---|---|
| Presenter status | Faculty/Staff |