Shape Coexistence and the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">N</mml:mi><mml:mi mathvariant="italic" /><mml:mspace /><mml:mo>=</mml:mo><mml:mspace /><mml:mn>28</mml:mn><mml:mn /></mml:math>Shell Closure Far from Stability

Sarazin, F.; Savajols, H.; Mittig, W.; Nowacki, F.; Orr, N. A.; Ren, Zhongzhou; Roussel‐Chomaz, P.; Auger, G.; Baiborodin, D.; Belozyorov, A. V.; Borcea, C.; Caurier, E.; Dlouhý, Z.; Gillibert, A.; Lalleman, A. S.; Lewitowicz, M.; Lukyanov, S. M.; Oliveira, F. de; Penionzhkevich, Y. E.; Ridikas, D.; Sakuraï, H.; Tarasov, O.; Vismes, A. de

doi:10.1103/physrevlett.84.5062

Cited by 206 publications

(152 citation statements)

References 22 publications

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“…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].…”

supporting

confidence: 55%

Is the7/21−Isomer State ofS43Spherical?

Chevrier¹,

Daugas²,

Gaudefroy³

et al. 2012

Phys. Rev. Lett.

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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 ...

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supporting

confidence: 55%

Is the7/21−Isomer State ofS43Spherical?

Chevrier¹,

Daugas²,

Gaudefroy³

et al. 2012

Phys. Rev. Lett.

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“…This has been confirmed in subsequent intermediate energy Coulomb excitation studies [49][50][51]. More recent experiments on nuclei of this region [52,53] suggest that 44 S is indeed a deformed nucleus but with strong shape coexistence making more challenging its theoretical description.…”

Section: Introductionsupporting

confidence: 48%

Correlations beyond the mean field in magnesium isotopes: angular momentum projection and configuration mixing

2002

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The quadrupole deformation properties of the ground and low-lying excited states of the even-even Magnesium isotopes with N ranging from 8 to 28 have been studied in the framework of the angular momentum projected generator coordinate method with the Gogny force. It is shown that the N=8 neutron magic number is preserved (in a dynamical sense) in 20 Mg leading to a spherical ground state. For the magic numbers N=20 and N=28 this is not the case and prolate deformed ground states are obtained. The method yields values of the two neutron separation energies which are in much better agreement with experiment than those obtained at the mean field level. It is also obtained that 40 Mg is at the neutron dripline. Concerning the results for the excitation energies of the 2 + excited states and their transition probabilities to the ground state we observe a good agreement with the available experimental data. On the theoretical side, we also present a detailed justification of the prescription used for the density dependent part of the interaction in our beyond-mean-field calculations.

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“…The erosion of the shell gap and the migration of neutron magic numbers such as N = 8 [1] and 20 [2] far from stability have been important and fascinating subjects in nuclear structure physics [3]. The N = 28 shell closure in neutron-rich Si and S isotopes has received considerable experimental [4][5][6][7][8][9][10][11][12][13] and theoretical attention [14][15][16][17][18][19][20][21][22][23]. Experimental data [5,6,[8][9][10][11] indicate gradual quenching of the N = 28 shell gap toward neutron-rich isotones and the onset of deformation in N ≈ 28 S and Si isotopes.…”

mentioning

confidence: 99%

Prolate, oblate, and triaxial shape coexistence, and the lost magicity ofN=28in43S

et al. 2013

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We report the low-lying spectrum and collective β and γ deformation of 43 S as investigated by antisymmetrized molecular dynamics. Our result successfully explains the observed data including an isomeric 7/2 − 1 state and illustrates the coexistence of the prolate-deformed ground band with a vanishing N = 28 shell gap, a triaxially deformed isomeric state, and an oblate-deformed excited band at very low excitation energies. The erosion of the shell gap and the migration of neutron magic numbers such as N = 8 [1] and 20 [2] far from stability have been important and fascinating subjects in nuclear structure physics [3]. The N = 28 shell closure in neutron-rich Si and S isotopes has received considerable experimental [4][5][6][7][8][9][10][11][12][13] and theoretical attention [14][15][16][17][18][19][20][21][22][23]. Experimental data [5,6,[8][9][10][11] indicate gradual quenching of the N = 28 shell gap toward neutron-rich isotones and the onset of deformation in N ≈ 28 S and Si isotopes. Unlike the case of smaller magic numbers, the neutron single-particle levels f 7/2 and p 3/2 that compose the N = 28 shell gap belong to the same major shell in the absence of spin-orbit splitting, and their angular momentum differs by 2. Therefore, we can expect that quenching of the N = 28 shell gap induces strong quadrupole correlations, which will lead to the coexistence of various deformed states [24]. For example, observation of low-lying states [25] and theoretical calculations [22,23] suggest shape coexistence in 44 S. In the vicinity of 44 S, 43 S is of particular importance and interest for the following reasons. First, 43 S has an odd number of neutrons. Thus, its low-lying spectrum provides direct information on the neutron single-particle levels. Second, and more importantly, it is believed to have a prolate-deformed ground state and a very low-lying isomeric 7/2 − 1 state at 319 keV, which has been interpreted in the shell model framework as resulting from an inversion of the normal (νf 7/2 ) −1 and deformed intruder (νp 3/2 ) 1 configurations [12]. More recently, measurement of the electric quadrupole moment of the 7/2 − 1 state [26] has shown that it deviates from the pure spherical (νf 7/2 ) −1 configuration, suggesting possible shape coexistence driven by quenching of the N = 28 shell gap and the resulting strong quadrupole correlation. Therefore, a theoretical calculation that can describe the quadrupole collectivity in a large model space is essential for revealing the nature of this shape coexistence far from stability.In this Rapid Communication, we report triaxial deformation of the isomeric 7/2 − 1 state and the shape coexistence of prolate, triaxial, and oblate deformation of 43 S at excitation energies of less than 2 MeV. We apply the antisymmetrized molecular dynamics (AMD), which has already been successfully applied to the breaking of neutron magic number N = 8 [27][28][29] and 20 [30][31][32], combined with the generator coordinate method (GCM) using generator coordinates of the quadrupole deforma...

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Shape Coexistence and theN=28Shell Closure Far from Stability

Cited by 206 publications

References 22 publications

Is the7/21−Isomer State ofS43Spherical?

Is the7/21−Isomer State ofS43Spherical?

Correlations beyond the mean field in magnesium isotopes: angular momentum projection and configuration mixing

Prolate, oblate, and triaxial shape coexistence, and the lost magicity ofN=28in43S

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