Shape transitions in exotic Si and S isotopes and tensor-force-driven Jahn-Teller effect

Utsuno, Yutaka; Otsuka, Takaharu; Brown, B. A.; Honma, Michio; Mizusaki, T.; Shimizu, Noritaka

doi:10.1103/physrevc.86.051301

Cited by 190 publications

(294 citation statements)

References 49 publications

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“…This spin and parity has been used to explain the data of β decay [19] as well as the knockout experiment [29]. A number of excited states of this nucleus have been populated [23] by proton knockout, and the states have been interpreted in the light of the SDPF-MU interaction [41]. According to the conventional shell model with neutron number N = 22, the valence neutron should occupy the f 7/2 orbital.…”

Section: Discussionmentioning

confidence: 99%

Ground-state configuration of neutron-rich Al35 via Coulomb breakup

Chakraborty¹,

Pramanik²,

Aumann³

et al. 2017

Phys. Rev. C

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The ground-state configuration of 35 Al has been studied via Coulomb dissociation (CD) using the LAND-FRS setup (GSI, Darmstadt) at a relativistic energy of ∼403 MeV/nucleon. The measured inclusive differential CD cross section for 35 Al, integrated up to 5.0 MeV relative energy between the 34 Al core and the neutron using a Pb target, is 78(13) mb. The exclusive measured CD cross section that populates various excited states of 34 Al is 29(7) mb. The differential CD cross section of 35 Al → 34 Al + n has been interpreted in the light of a direct breakup model, and it suggests that the possible ground-state spin and parity of 35 Al could be, tentatively, 1/2 + or 3/2 + or 5/2 + . The valence neutrons, in the ground state of 35 Al, may occupy a combination of either l = 3,0 or l = 1,2 orbitals coupled with the 34 Al core in the ground and isomeric state(s), respectively. This hints of a particle-hole configuration of the neutron across the magic shell gaps at N = 20,28 which suggests narrowing the magic shell gap. If the 5/2 + is the ground-state spin-parity of 35 Al as suggested in the literature, then the major ground-state configuration of 35 Al is a combination of 34 Al(g.s.; 4 − ) ⊗ ν p 3/2 and 34 Al(isomer; 1 + ) ⊗ ν d 3/2 states. The result from this experiment has been compared with that from a previous knockout measurement and a calculation using the SDPF-M interaction.

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Section: Discussionmentioning

confidence: 99%

Ground-state configuration of neutron-rich Al35 via Coulomb breakup

Chakraborty¹,

Pramanik²,

Aumann³

et al. 2017

Phys. Rev. C

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“…While without further information, such as exclusive σ 44→42 (0 + 1 ) and/or σ 44→42 (0 + 2 ) measurements, we cannot uniquely constrain the predominant shapes of these ground states, it is clear from Fig. 2 [3] and supported by the schematic explanation of shapes provided in the analysis of Utsuno [14], then the two-state analysis predicts 40 Mg will have a dominantly prolate deformation. The change in the dominant ground-state configuration becomes more clear with larger cross-section ratios, R.…”

mentioning

confidence: 94%

“…Removing d 3/2 protons simultaneously reduces the effect of the repulsive πd 3/2 -νf 5/2 and attractive πd 3/2 -νf 7/2 interactions, which effectively pushes the two neutron f shells closer in energy [17]. At the same time, at N = 28 the spacing between the proton πd 5/2 , πs 1/2 , and πd 3/2 orbitals is narrowed [14,[18][19][20]. With the narrowing of the N = 28 gap and the proton single-particle spacings, quadrupole excitations develop between the l = 2 νp 3/2 and νf 7/2 neutron orbitals and the πd 5/2 and πs 1/2 proton orbitals, resulting in well-deformed nuclear shapes.…”

mentioning

confidence: 99%

“…[12,13]. In the present analysis, shell model TNAs connecting states in 42 Si and 40 Mg were calculated using the recently proposed SDPF-MU effective interaction [14]. The interaction is well tested in the region of neutron-rich nuclei below 48 Ca, reproducing 2 + 1 and 4 + 1 energies, as well as B(E2) values in the S and Si isotopes approaching N = 28 [15].…”

mentioning

confidence: 99%

“…A schematic understanding of the evolution of the shapes along the N = 28 isotones has been proposed [14] in terms of the quadrupole force driving mixing between m = ±1/2 substates in the near-degenerate proton s 1/2 and d 5/2 (or d 3/2 ) orbitals and changing the occupancy of the prolate-driving l = 2, m = ±1/2 substates [14]. For 44 16 S, data and calculations [21][22][23][24][25][26][27] indicate well-developed prolate deformation in the ground state, accompanied by a coexisting spherical 0 + 2 excited state.…”

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confidence: 99%

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Shell and shape evolution atN=28: TheMg40ground state

Crawford¹,

Fallon²,

Macchiavelli³

et al. 2014

Phys. Rev. C

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A measurement of the direct two-proton removal from 42 Si has provided the first structural information on the N = 28 isotone 40 Mg. The value for the inclusive cross section for two-proton removal from 42 Si of 40 +27 −17 μb is significantly lower than that predicted by structure calculations using the recent SDPF-MU shell-model effective interaction combined with eikonal reaction theory. This observed discrepancy is consistent with the interpretation that only one of the predicted low-lying 0 + states in 40 Mg is bound. A two-state mixing analysis describing two-proton knockout cross sections along N = 28 provides support for the interpretation of a prolate-deformed 40 The study of nuclei far from the line of β stability is one of the most active and challenging areas of current nuclear structure physics. Exotic combinations of protons (Z) and neutrons (N ) can significantly affect the underlying shell structure, and for weakly bound nuclei at or near the dripline, the proximity to continuum states may further alter nuclear properties. Benchmarking and constraining theory at the very limits of existence is critical, and one of the most exotic neutron-rich nuclei currently accessible to experiment is 40 Mg.First observed following fragmentation of a 48 Ca primary beam at the National Superconducting Cyclotron Laboratory in 2007 (with three events) [1], 40 12 Mg 28 lies at an intersection for nucleon magic numbers and the neutron dripline. It is expected to exhibit [2] the collective and deformed properties characteristic of the N = 28 isotones below 48 Ca, which is a region of rapidly changing nuclear shapes. Large-scale shell-model calculations predict that 40 Mg should be a welldeformed prolate rotor [3]. In addition, the last bound neutron orbital is expected to be the low-l p 3/2 state, leading to the possibility that weak binding effects could play a role.Further, deformation along the Z = 12 isotopic chain has been of recent experimental interest, with the work of Doornenbal et al. [4], in which an extended region of deformation in the Mg isotopes from the quenched N = 20 gap out to N = 26 is observed, as determined by the ratio of E(4 + 1 )/E(2 + 1 ), and is expected to persist at N = 28. We present here the first experimental structure information on 40 Mg following measurement of the inclusive two-proton removal cross section from 42 Si and discuss the results as a part of the overall shape evolution along the N = 28 isotonic chain. We provide a limit on the number of bound states predicted by theory, and evidence supporting a prolate-deformed 40 Mg ground state based on a two-state mixing model.One-and two-proton knockout reactions from 42 Si were carried out at Radioactive Isotope Beam Factory (RIBF), operated by RIKEN Nishina Center and the Center for Nuclear Study, University of Tokyo. A primary beam of 48 Ca, at an energy of 345 MeV/nucleon, with an average intensity of approximately 70 pnA, was fragmented in a thick (15-mm) rotating Be production target to produce a cocktail of projectile...

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Discussion of the d(28Mg,p)29Mg Experiment and Conclusions

MacGregor

2022

Springer Theses

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Shape transitions in exotic Si and S isotopes and tensor-force-driven Jahn-Teller effect

Cited by 190 publications

References 49 publications

Ground-state configuration of neutron-rich Al35 via Coulomb breakup

Ground-state configuration of neutron-rich Al35 via Coulomb breakup

Shell and shape evolution atN=28: TheMg40ground state

Discussion of the d(28Mg,p)29Mg Experiment and Conclusions

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