Proton Shell Gaps in N=28 Nuclei from the First Complete Spectroscopy Study with FRIB Decay Station Initiator

• Published in: Physical review letters 2024-04, Vol.132 (15), p.152503-152503, Article 152503
• Main Authors: Cox, I, Xu, Z Y, Grzywacz, R, Ong, W-J, Rasco, B C, Kitamura, N, Hoskins, D, Neupane, S, Ruland, T J, Allmond, J M, King, T T, Lubna, R S, Rykaczewski, K P, Schatz, H, Sherrill, B M, Tarasov, O B, Ayangeakaa, A D, Berg, H C, Bleuel, D L, Cerizza, G, Christie, J, Chester, A, Davis, J, Dembski, C, Doetsch, A A, Duarte, J G, Estrade, A, Fijałkowska, A, Gray, T J, Good, E C, Haak, K, Hanai, S, Harke, J T, Harris, C, Hermansen, K, Hoff, D E M, Jain, R, Karny, M, Kolos, K, Laminack, A, Liddick, S N, Longfellow, B, Lyons, S, Madurga, M, Mogannam, M J, Nowicki, A, Ogunbeku, T H, Owens-Fryar, G, Rajabali, M M, Richard, A L, Ronning, E K, Rose, G E, Siegl, K, Singh, M, Spyrou, A, Sweet, A, Tsantiri, A, Walters, W B, Yokoyama, R
• Format: Article
• Language: English
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.132.152503

The first complete measurement of the β-decay strength distribution of _{17}^{45}Cl_{28} was performed at the Facility for Rare Isotope Beams (FRIB) with the FRIB Decay Station Initiator during the second FRIB experiment. The measurement involved the detection of neutrons and γ rays in two focal planes of the FRIB Decay Station Initiator in a single experiment for the first time. This enabled an analytical consistency in extracting the β-decay strength distribution over the large range of excitation energies, including neutron unbound states. We observe a rapid increase in the β-decay strength distribution above the neutron separation energy in _{18}^{45}Ar_{27}. This was interpreted to be caused by the transitioning of neutrons into protons excited across the Z=20 shell gap. The SDPF-MU interaction with reduced shell gap best reproduced the data. The measurement demonstrates a new approach that is sensitive to the proton shell gap in neutron rich nuclei according to SDPF-MU calculations.