Abstract
We observed a new isomeric γ transition at 168 keV in Mg36, with a half-life of T1/2=90(-50+410) ns. We propose that the observed transition deexcites a new 0+ isomeric state at 833 keV and populates the previously known first 2+ state. The existence of this isomer is consistent with the predictions of the large-scale shell-model calculations of Mg36 using the sdpf-u-mix interaction. The observed excitation energy of the second 0+ state is caused by the small energy separation between two prolate-deformed configurations where the intruder configuration corresponds to two-neutron excitations from the sd to the pf shell. Within this interpretation, Mg36 becomes the crossing point between nuclei in which ground state deformed/superdeformed configurations are caused by the dominance of N=20 intruders (Mg32,34) and nuclei where deformed configurations are associated with the breaking of the N=28 closure and a large occupancy of the 1p3/2 neutron orbit (Mg38 and beyond). We found the lack of three-body monopole corrections in other effective interactions results in a predominance of N=20 intruder configurations past Mg38 incompatible with our observation. We conclude that Mg36 bridges the N=20 and N=28 islands of inversion, forming the so-called big island of deformation.
| Original language | English |
|---|---|
| Article number | L061301 |
| Journal | Physical Review C |
| Volume | 109 |
| Issue number | 6 |
| DOIs | |
| State | Published - Jun 2024 |
Funding
Acknowledgments. We thank Augusto Macchiavelli for the fruitful discussions during the preparation of the manuscript. The isotope(s) used in this research was supplied by the Isotope Program within the Office of Nuclear Physics in the Department of Energy's Office of Science. The Lanczos shell-model calculation using the EEdf1 interaction was performed with the code kshell . This research was sponsored in part by the National Nuclear Security Administration under the Stewardship Science Academic Alliances program through DOE Cooperative Agreements No. DOE DE-NA0003899 and No. DE-NA0004068. This research was also sponsored by the Office of Nuclear Physics, U.S. Department of Energy, under Contracts No. DE-FG02-96ER40983 (UT) and No. DE-SC0020451 (MSU). This research was sponsored in part by the National Science Foundation under the Contract No. NSF-MRI-1919735. This work was also supported by the National Nuclear Security Administration through the Nuclear Science and Security Consortium under Award No. DE-NA0003180 and the Stewardship Science Academic Alliances program through U.S. DOE Award No. DOE-DE-NA0003906. N.S. and Y.U. acknowledge computer resources provided by the U. Tsukuba MCRP program (woi22i022) and the \u201CProgram for Promoting Researches on the Supercomputer Fugaku\u201D (Grant No. JPMXP1020200105). A.P. is supported by Grant No. CEX2020-001007-S funded by MCIN/AEI/10.13039/501100011033 and PID2021-127890NB-I00.