Speaker
Description
Understanding how nuclear structure evolves at the limits of stability is a central goal of modern radioactive ion beam facilities. In regions of extreme neutron excess, traditional shell closures weaken and intruder configurations and deformation can emerge. β-decay spectroscopy provides a powerful probe of these systems, particularly when production rates are extremely low and other spectroscopic approaches are impractical. This work highlights recent results from two experiments performed at the Facility for Rare Isotope Beams (FRIB) using the FRIB Decay Station initiator (FDSi), a modular decay spectroscopy system designed to correlate implanted ions with their subsequent β decays, delayed γ rays, and β-delayed neutrons.
The first study reports the first measurements of the β-decay half-lives of the neutron-rich nuclei 31F and 37Na, which lie near the neutron drip line and the N=20 island-of-inversion region. Using event-by-event implant–decay correlations, half-lives of approximately 1–2 ms were determined, among the shortest observed in this region of the nuclear chart. Comparisons with theoretical calculations show that while global models reproduce the general scale of the half-lives, they do not capture the systematics of neighboring isotopes, highlighting the importance of new experimental benchmarks. A second experiment focuses on delayed γ-ray spectroscopy of neutron-rich cobalt isotopes approaching N=50. In this study, a 202(20) µs isomer in 73Co was identified through a 1178 keV transition associated with a deformed proton intruder configuration across the Z=28 shell gap. Comparisons with theory indicate that the spherical 7/2- configuration remains the ground state, suggesting that a proton-driven shape inversion does not occur in cobalt isotopes as N=50 is approached.
This presentation will describe the design and capabilities of FDSi and the experimental techniques used to correlate implanted ions with subsequent decay signatures. Results from these two early FRIB experiments will be summarized, including the first half-life measurements of 31F and 37Na and new observation of a microsecond isomer in 73Co. These studies illustrate the range of decay measurements accessible with FDSi, from millisecond β-decay half-lives to microsecond isomeric transitions, and represent some of the new results from ongoing programs that will continue to expand decay spectroscopy studies of nuclei at the limits of stability.
| Contribution category | Experiment |
|---|---|
| Presenter status | Faculty/Staff |