The 0 þ 2 state in 34 Si has been populated at the GANIL-LISE3 facility through the decay of a newly discovered 1 þ isomer in 34 Al of 26(1) ms half-life. The simultaneous detection of e þ e À pairs allowed the determination of the excitation energy Eð0 þ 2 Þ ¼ 2719ð3Þ keV and the half-life T 1=2 ¼ 19:4ð7Þ ns, from which an electric monopole strength of 2 ðE0Þ ¼ 13:0ð0:9Þ Â 10 À3 was deduced. The 2 þ 1 state is observed to decay both to the 0 þ 1 ground state and to the newly observed 0 þ 2 state [via a 607(2) keV transition] with a ratio Rð2Gathering all information, a weak mixing with the 0 þ 1 and a large deformation parameter of ¼ 0:29ð4Þ are found for the 0 þ 2 state, in good agreement with shell model calculations using a new SDPF-U-MIX interaction allowing np-nh excitations across the N ¼ 20 shell gap.
The electric quadrupole moment of the 33 13 Al 20 ground state, located at the border of the island of inversion, was obtained using continuous-beam β-detected nuclear quadrupole resonance (β-NQR). From the measured quadrupole coupling constant ν Q = 2.31(4) MHz in an α-Al 2 O 3 crystal, a precise value for the electric quadrupole moment is extracted: |Q s ( 33 Al)| = 141(3) mb. A comparison with large-scale shell model calculations shows that 33 Al has at least 50% intruder configurations in the ground state wave function, favoring the excitation of two neutrons across the N = 20 shell gap.33 Al therefore clearly marks the gradual transition north of the deformed Na and Mg nuclei towards the normal Z 14 isotopes.
We report on the spectroscopic quadrupole moment measurement of the 7=2 À 1 isomeric state in 43 16 S 27 [E Ã ¼ 320:5ð5Þ keV, T 1=2 ¼ 415ð3Þ ns], using the time dependent perturbed angular distribution technique at the RIKEN RIBF facility. Our value, j Q s j¼ 23ð3Þ efm 2 , is larger than that expected for a singleparticle state. Shell model calculations using the modern SDPF-U interaction for this mass region reproduce remarkably well the measured j Q s j , and show that non-negligible correlations drive the isomeric state away from a purely spherical shape. Thanks to recent developments of intense radioactive beams, unexplored landscapes of the Ségré chart such as the structure of nuclei far from the stability line can now be investigated in detail. One of the most striking results from the two last decades is the modification or disappearance of the so-called ''magic numbers'' in exotic nuclei. The first evidence for such structure modification was observed in N ¼ 20 neutron-rich nuclei [1]. Similar information has been found for exotic nuclei around N ¼ 28 [2]. For the latter nuclei, the set of available theoretical [3,4] and experimental [5][6][7][8][9] data provide a coherent description of the gradual erosion of the N ¼ 28 gap and the onset of deformation from the spherical 48 Ca nucleus towards the neutron-rich and oblate deformed 42 Si nucleus [10]. Midway from these two extremes lie the sulfur isotopes of transitional nature, for which spherical or deformed shape coexistence is expected in 43;44 S mainly based on theoretical interpretations of recent experimental data [11,12]. However, no definitive experimental evidence assess shape coexistence in these isotopes. Within the shell model (SM) framework, shape transitions in this mass region reflect the strong increase of correlation energy while moving away from the stability line [13,14]. From a recent interpretation of in-beam -ray spectroscopy data in exotic Si isotopes, the aforementioned increase of the correlation energy was mainly ascribed to proton-neutron interactions [15]. The latter would be responsible for the inversion between natural (i.e., rather spherical) and intruder (i.e., deformed) configurations in both 43;44 S. For the 43 S isomeric state [E Ã ¼ 320:5ð5Þ keV, T 1=2 ¼ 415ð4Þ ns], the spin-parity J ¼ 7=2 À resulting from the natural orbital configuration ð f 7=2 Þ À1 can be inferred from the very good agreement of SM calculations with the recently measured magnetic moment [g exp ¼ À0:317ð4Þ, g SM ¼ À0:280] [12]. The SM furthermore predicts that this normal configuration coexists with the intruder prolate deformed 3=2 À ground state (g.s.).In order to verify this scenario in 43 S, two experimental observations are still missing: (i) evidence for the rotational band built on top of the suspected intruder prolate ground state of the nucleus and (ii) determination of the rather spherical nature of the isomeric state. In this Letter we report on the measurement of the spectroscopic quadrupole moment of the 7=2 À 1 isomeric state using the ...
The degree of freedom of spin in quantum systems serves as an unparalleled laboratory where intriguing quantum physical properties can be observed, and the ability to control spin is a powerful tool in physics research. We propose a novel method for controlling spin in a system of rare isotopes which takes advantage of the mechanism of the projectile fragmentation reaction combined with the momentum-dispersion matching technique. The present method was verified in an experiment at the RIKEN RI Beam Factory, in which a degree of alignment of 8% was achieved for the spin of a rare isotope Al-32. The figure of merit for the present method was found to be greater than that of the conventional method by a factor of more than 50.Comment: 18 pages, 5 figure
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.