Onset of intruder ground state in exotic<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Na</mml:mi></mml:mrow></mml:math>isotopes and evolution of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>20</mml:mn></mml:mrow></mml:math>shell gap

Utsuno, Yutaka; Otsuka, Takaharu; Glasmacher, T.; Mizusaki, T.; Honma, Michio

doi:10.1103/physrevc.70.044307

Cited by 158 publications

(129 citation statements)

References 42 publications

(191 reference statements)

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“…They used an eikonal reaction model and Woods-Saxon overlap functions, that were calculated with a well depth adjusted to reproduce the one-neutron separation energies. The results were compared with shell model predictions using the fitted sd-shell USDB interaction [7] and the SDPF-M interaction [8]. The theoretical calculations corroborate the large s-wave probability found in the experimental analysis, implying thereby that 24 O is indeed a doubly magic nucleus.…”

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confidence: 53%

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Closed-shell properties ofO24withab initiocoupled-cluster theory

et al. 2011

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We present a microscopic calculation of spectroscopic factors for neutron and proton removal from 24 O using the coupled-cluster method and a state-of-the-art chiral nucleon-nucleon interaction at next-to-next-to-next-to-leading order. In order to account for the coupling to the scattering continuum we use a Berggren single-particle basis that treats bound, resonant, and continuum states on an equal footing. We report neutron removal spectroscopic factors for the 23 O states J π = 1/2 + , 5/2 + , 3/2 − and 1/2 − , and proton removal spectroscopic factors for the 23 N states 1/2 − and 3/2 − . Our calculations support the accumulated experimental evidence that 24 O is a closed-shell nucleus.PACS numbers: 21.10.Jx, 21.60. De, 21.10.Pc, 31.15.bw, 24.10.Cn Introduction The study of nuclei far from stability is a leading direction in nuclear physics, experimentally and theoretically. It represents a considerable intellectual challenge to our understanding of the stability of matter itself, with potential implications for the synthesis of elements. An important aspect of this research direction is to understand how magic numbers and shells appear and evolve with increasing numbers of neutrons or protons. The structure and properties of barely stable nuclei at the limits of stability, have been demonstrated to deviate dramatically from the established patterns for ordinary and stable nuclei, see Ref.[1] and references therein for a recent review. One of the striking features of nuclei close to the drip line is the adjustment of shell gaps, giving rise to different magic numbers [2]. The way shell closures and single-particle properties evolve as functions of the number of nucleons forms one of the greatest challenges to our understanding of the basic features of nuclei, and thereby the stability of matter.The chain of oxygen isotopes up to 28 O is particularly interesting since these are the heaviest nuclei for which the drip line is well established. Two out of four stable even-even isotopes exhibit a doubly magic nature, namely 22 O (Z=8,N =14) and 24 O (Z=8, N =16). Several recent experiments [3-6] bring evidence that 24 O is the last stable oxygen isotope. This is remarkable, in particular if one considers the fact that the addition of a single proton on top of the Z = 8 closed shell brings the drip line of the fluorine isotopes to 31 F. Recent measurements [3] also suggest that 24 O has a spherical neutron configuration. The isotopes 25−28 O are all believed to be unstable towards neutron emission, even though 28 O is a doubly magic nucleus within the standard shell-model picture. This indicates that the magic number at the neutron drip line for the oxygen isotopes is not at N = 20 but rather at N = 16.Although spectroscopic factors are not observable quantities [9,10], they can be used to address shell closure properties within the context of a given model. Experimentally, spectroscopic factors are defined as the ratio of the observed reaction rate with respect to the same

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confidence: 53%

“…The above mentioned theoretical calculations of Refs. [7,8] involve only fitted effective interactions tailored to small shell-model spaces, such as the sd or the sd − pf shells only.…”

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confidence: 99%

Closed-shell properties ofO24withab initiocoupled-cluster theory

et al. 2011

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“…For instance the spin-orbit coupling may be reduced by neutrons skin appearance, or in the light nuclei the interaction between bound orbitals and continuum states can modify the energy gaps. The D1S parameterization fails to reproduce the N = 20 single particle energy spectra in exotic nuclei in the O, Ne, or Mg chains [43,44,45,46]; one would expect some improvement from a new Gogny + tensor parameterization on that matter. Besides, since the tensor force may modify considerably the single particle energies, all the nuclear structure properties can be affected.…”

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confidence: 99%

Interplay between tensor force and deformation in even–even nuclei

Bernard

Anguiano

2016

Nuclear Physics A

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In this work we study the effect of the nuclear tensor force on properties related with deformation. We focus on isotopes in the Mg, Si, S, Ar, Sr and Zr chains within the Hartree-Fock-Bogoliubov theory using the D1ST2a Gogny interaction. Contributions to the tensor energy in terms of saturated and unsaturated subshells are analyzed. Like-particle and proton-neutron parts of the tensor term are independently examinated. We found that the tensor term may considerably modify the potential energy landscapes and change the ground state shape. We analyze too how the pairing characteristics of the ground state change when the tensor force is included.

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“…The change in shell structure around N = 20 is now known to be a result of the tensor force, which is strongly attractive for the spin flip pairs πd 5/2 -νd 3/2 and strongly repulsive for the pairs πd 5/2 -ν f 7/2 [5][6][7]. For nuclei in the region of N ∼ 20 and Z 13, the reduced N = 20 gap allows p f shell intruder configurations, in the form of multi-particle, multi-hole (npnh or nℏω) cross shell excitations, to compete with standard sd only configurations if the gain in correlation energy is on the same order as the size of the shell gap [8][9][10]. This has led to the establishment of the "island of inversion"-a region of nuclei near N = 20 for which the intruder configuration is dominant in the ground state.…”

mentioning

confidence: 99%

“…The measured 28 F ground state energy is in good agreement with USDA/USDB shell model predictions, indicating that p f shell intruder configurations play only a small role in the ground state structure of 28 F and establishing a low-Z boundary of the island of inversion for N = 19 isotones. A hallmark of the nuclear shell model is its reproduction of large energy gaps at nucleon numbers 2,8,20,28,50,82, and 126. Although well established in stable nuclei, these magic numbers begin to disappear for nuclei far from stability.…”

mentioning

confidence: 99%

Exploring the Low-ZShore of the Island of Inversion atN=19

Christian¹,

Frank²,

Ash³

et al. 2012

Phys. Rev. Lett.

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The technique of invariant mass spectroscopy has been used to measure, for the first time, the ground state energy of neutron-unbound 28 F, determined to be a resonance in the 27 F + n continuum at 220(50) keV. States in 28 F were populated by the reactions of a 62 MeV/u 29 Ne beam impinging on a 288 mg/cm 2 beryllium target. The measured 28 F ground state energy is in good agreement with USDA/USDB shell model predictions, indicating that p f shell intruder configurations play only a small role in the ground state structure of 28 F and establishing a low-Z boundary of the island of inversion for N = 19 isotones.PACS numbers: 21.10.Dr, 21.10.Pc A hallmark of the nuclear shell model is its reproduction of large energy gaps at nucleon numbers 2, 8, 20, 28, 50, 82, and 126. Although well established in stable nuclei, these magic numbers begin to disappear for nuclei far from stability. For example, it has been known for over 30 years that the large shell gap at N = 20 diminishes for neutron-rich nuclei [1][2][3][4]. The change in shell structure around N = 20 is now known to be a result of the tensor force, which is strongly attractive for the spin flip pairs πd 5/2 -νd 3/2 and strongly repulsive for the pairs πd 5/2 -ν f 7/2 [5][6][7]. For nuclei in the region of N ∼ 20 and Z 13, the reduced N = 20 gap allows p f shell intruder configurations, in the form of multi-particle, multi-hole (npnh or nℏω) cross shell excitations, to compete with standard sd only configurations if the gain in correlation energy is on the same order as the size of the shell gap [8][9][10]. This has led to the establishment of the "island of inversion"-a region of nuclei near N = 20 for which the intruder configuration is dominant in the ground state.

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Onset of intruder ground state in exoticNaisotopes and evolution of theN=20shell gap

Cited by 158 publications

References 42 publications

Closed-shell properties ofO24withab initiocoupled-cluster theory

Closed-shell properties ofO24withab initiocoupled-cluster theory

Interplay between tensor force and deformation in even–even nuclei

Exploring the Low-ZShore of the Island of Inversion atN=19

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