Abstract
Excited-state spectroscopy from the first experiment at the Facility for Rare Isotope Beams (FRIB) is reported. A 24(2)-μs isomer was observed with the FRIB Decay Station initiator (FDSi) through a cascade of 224- and 401-keV γ rays in coincidence with Na32 nuclei. This is the only known microsecond isomer (1 μs≤T1/2<1 ms) in the region. This nucleus is at the heart of the N=20 island of shape inversion and is at the crossroads of the spherical shell-model, deformed shell-model, and ab initio theories. It can be represented as the coupling of a proton hole and neutron particle to Mg32, Mg32+π-1+ν+1. This odd-odd coupling and isomer formation provides a sensitive measure of the underlying shape degrees of freedom of Mg32, where the onset of spherical-to-deformed shape inversion begins with a low-lying deformed 2+ state at 885 keV and a low-lying shape-coexisting 02+ state at 1058 keV. We suggest two possible explanations for the 625-keV isomer in Na32: a 6- spherical shape isomer that decays by E2 or a 0+ deformed spin isomer that decays by M2. The present results and calculations are most consistent with the latter, indicating that the low-lying states are dominated by deformation.
| Original language | English |
|---|---|
| Article number | 242501 |
| Journal | Physical Review Letters |
| Volume | 130 |
| Issue number | 24 |
| DOIs | |
| State | Published - Jun 16 2023 |
Funding
Many thanks to B. A. Brown and B. M. Sherrill for helpful discussions. This material is based upon work supported in part by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Contracts No. DE-AC02-06CH11357 (ANL), No. DE-AC02-98CH10946 (BNL), No. DE-AC02-05CH11231 (LBNL), No. DE-AC52-07NA27344 (LLNL), DE-SC0020451 (Michigan State), No. DE-SC0014448 (Mississippi State), No. DE-AC05-00OR22725 (ORNL), and No. DE-FG02-96ER40983 (UTK). The publisher acknowledges the U.S. government license to provide public access under the DOE Public Access Plan . This work was also supported by the U.S. National Science Foundation under Grants No. PHY-2012522 (FSU) and No. PHY-1848177 (CAREER) (Mississippi State). The research was also sponsored by the U.S. Department of Energy, National Nuclear Security Administration under Award No. DE-NA0003180 (Michigan State) and the Stewardship Science Academic Alliances program through DOE Award No. DE-NA0003899 (UTK) and No. DOE-DE-NA0003906 (Michigan State), and NSF Major Research Instrumentation Program Grant No. 1919735 (UTK). A. Poves acknowledges the support of grant CEX2020-001007-S funded by MCIN/AEI and PID2021-127890NB-I00. This work was supported in part by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project-ID 279384907—SFB 1245. The VS-IMSRG calculations were in part performed with an allocation of computing resources at the Jülich Supercomputing Center. This research was supported in part by Australian Research Council Grant No. DP210101201. This research used resources of the Facility for Rare Isotope Beams, which is a DOE Office of Science User Facility.
| Funders | Funder number |
|---|---|
| National Science Foundation | CEX2020-001007-S, PHY-2012522, 1919735 |
| U.S. Department of Energy | |
| Albert Ellis Institute | PID2021-127890NB-I00 |
| Office of Science | |
| National Nuclear Security Administration | DE-NA0003180, DE-NA0003899, DOE-DE-NA0003906 |
| Nuclear Physics | DE-AC02-06CH11357 |
| Argonne National Laboratory | DE-AC02-05CH11231, DE-AC02-98CH10946 |
| Lawrence Livermore National Laboratory | DE-SC0020451, DE-AC05-00OR22725, DE-SC0014448 |
| Oak Ridge National Laboratory | DE-FG02-96ER40983 |
| Lawrence Berkeley National Laboratory | DE-AC52-07NA27344 |
| Florida State University | PHY-1848177 |
| Australian Research Council | DP210101201 |
| Deutsche Forschungsgemeinschaft | 279384907—SFB 1245 |
| Ministerio de Ciencia e Innovación |