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

I Cox; Z Y Xu; R Grzywacz; W-J Ong; B C Rasco; N Kitamura; D Hoskins; S Neupane; T J Ruland; J M Allmond; T T King; R S Lubna; K P Rykaczewski; H Schatz; B M Sherrill; O B Tarasov; A D Ayangeakaa; H C Berg; D L Bleuel; G Cerizza; J Christie; A Chester; J Davis; C Dembski; A A Doetsch; J G Duarte; A Estrade; A Fijałkowska; T J Gray; E C Good; K Haak; S Hanai; J T Harke; C Harris; K Hermansen; D E M Hoff; R Jain; M Karny; K Kolos; A Laminack; S N Liddick; B Longfellow; S Lyons; M Madurga; M J Mogannam; A Nowicki; T H Ogunbeku; G Owens-Fryar; M M Rajabali; A L Richard; E K Ronning; G E Rose; K Siegl; M Singh; A Spyrou; A Sweet; A Tsantiri; W B Walters; R Yokoyama

doi:10.1103/PhysRevLett.132.152503

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

Phys Rev Lett. 2024 Apr 12;132(15):152503. doi: 10.1103/PhysRevLett.132.152503.

Authors

I Cox¹, Z Y Xu¹, R Grzywacz^{1

2}, W-J Ong³, B C Rasco², N Kitamura¹, D Hoskins¹, S Neupane^{1

3}, T J Ruland^{2

4}, J M Allmond², T T King², R S Lubna⁵, K P Rykaczewski², H Schatz^{5

6}, B M Sherrill^{5

6}, O B Tarasov⁵, A D Ayangeakaa^{7

8}, H C Berg^{5

6}, D L Bleuel³, G Cerizza⁵, J Christie¹, A Chester⁵, J Davis⁹, C Dembski^{5

6}, A A Doetsch^{5

6}, J G Duarte³, A Estrade¹⁰, A Fijałkowska¹¹, T J Gray², E C Good⁵, K Haak⁶, S Hanai¹², J T Harke³, C Harris⁶, K Hermansen^{5

6}, D E M Hoff³, R Jain^{5

6}, M Karny¹¹, K Kolos³, A Laminack², S N Liddick^{5

13}, B Longfellow³, S Lyons⁹, M Madurga¹, M J Mogannam^{5

13}, A Nowicki¹, T H Ogunbeku³, G Owens-Fryar^{5

6}, M M Rajabali¹⁴, A L Richard³, E K Ronning^{5

13}, G E Rose¹⁵, K Siegl¹, M Singh^{1

16}, A Spyrou^{5

6}, A Sweet³, A Tsantiri^{5

6}, W B Walters¹⁷, R Yokoyama¹²

Affiliations

¹ Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.
² Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
³ Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
⁴ Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
⁵ Facility for Rare Isotope Beams, Michigan State University, East Lansing, Michigan 48824, USA.
⁶ Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA.
⁷ Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
⁸ Triangle Universities Nuclear Laboratory, Duke University, Durham, North Carolina 27708, USA.
⁹ Pacific Northwest National Laboratory, Richland, Washington 99354, USA.
¹⁰ Department of Physics, Central Michigan University, Mount Pleasant, Michigan 48859, USA.
¹¹ Faculty of Physics, University of Warsaw, PL 02-093 Warsaw, Poland.
¹² Center for Nuclear Study, University of Tokyo, Wako, Saitama 351-0198, Japan.
¹³ Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA.
¹⁴ Physics Department, Tennessee Technological University, Cookeville, Tennessee 38505, USA.
¹⁵ University of California, Berkeley, Berkeley, California 94704, USA.
¹⁶ Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
¹⁷ Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA.

PMID: 38682970
DOI: 10.1103/PhysRevLett.132.152503

Abstract

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.