First beta-delayed neutron spectroscopy of neutron-rich Cl isotopes with FDSi

The first experimental campaigns with FRIB Decay Station Initiator [1] at FRIB focused on the spectroscopy of very neutron-rich isotopes near the N=28 island of inversion. They provided a wealth of data on beta-delayed neutron emitters. We will present the first complete beta decay spectroscopy along the N=28 shell closure as it evolves from a spherical ⁴⁸Ca toward a strongly deformed ⁴²Si, using a combination of high-resolution neutron (NEXTi) and gamma-ray (DEGAi) data alongside total absorption spectroscopy data (MTAS). The beta-decay strength distribution of ⁴⁵Cl was extracted up to 8 MeV, including the feedings to both neutron bound and unbound states in ⁴⁵Ar, and is compared with the large-scale shell model calculations by Yohsida, et al. [2]. This experiment provides the first test of these predictions for the dominant Gamow-Teller transitions in this region. The importance of the discrepancies between model predictions and experimental data will be discussed, including a spin reassignment for the ground state in ⁴⁵Cl.



[1] https://fds.ornl.gov/initiator/

[2] S. Yoshida, Y. Utsuno, N. Shimizu, and T. Otsuka, Phys. Rev. C 97, 054321 (2018).