First β-Decay Half-Life Measurements of ³¹F and ³⁷Na Using FDSI

The Facility for Rare Isotope Beams (FRIB) has provided unprecedented access to isotopes far from stability, enabling

a detailed investigation of nuclear structure under extreme conditions. In this work, we report the first β-decay half-life

measurements of the neutron-rich isotopes ³¹F and ³⁷Na, where ³¹F is the most neutron-rich fluorine isotope observed

to date. These measurements were performed as part of a β-decay spectroscopy campaign using the FRIB Decay

Station Initiator (FDSI). Studying the β-decay properties of nuclei in this region offers critical insight into shell evolution

and structural changes driven by significant neutron-to-proton imbalance.

The reported results represent the shortest β-decay half-lives measured to date and serve as sensitive benchmarks

for theoretical shell-model calculations in the N = 28 region. The measured half-lives show good agreement with

predictions from the SDPFSDG shell-model interaction [1], reinforcing the role of advanced shell-model frameworks

in describing exotic nuclei. These findings demonstrate the capability of the FDSI setup to probe the most neutron-

rich systems accessible today and to deliver essential data for refining our understanding of nuclear forces and shell

evolution near the neutron drip line.

References

[1] S. Yosida et al., Phys. Rev. C 97, 054321; Erratum Phys. Rev. C 109, 029904 (2024)