The neutron-rich edge of the nuclear landscape: Experiment and theory.

Nowacki, F.; Obertelli, A.; Poves, A.

doi:10.1016/j.ppnp.2021.103866

“…The breakdown of the canonical magic numbers in unstable nuclei has attracted much attention over the years [1,2]. To date, the disappearance of magicity has been reported in several regions of the nuclear chart away from the stability line.…”

Section: Introductionmentioning

confidence: 99%

In-beam γ -ray spectroscopy of Mg32 via direct reactions

Kitamura¹,

Wimmer²,

Miyagi³

et al. 2022

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Background: The nucleus 32 Mg (N = 20 and Z = 12) plays a central role in the so-called "island of inversion" where in the ground states sd-shell neutrons are promoted to the f p-shell orbitals across the shell gap, resulting in the disappearance of the canonical neutron magic number N = 20.Purpose: The primary goals of this work are to extend the level scheme of 32 Mg, provide spin-parity assignments to excited states, and discuss the microscopic structure of each state through comparisons with theoretical calculations.Method: In-beam γ-ray spectroscopy of 32 Mg was performed using two direct-reaction probes, one-neutron (twoproton) knockout reactions on 33 Mg ( 34 Si). Final-state exclusive cross sections and parallel momentum distributions were extracted from the experimental data and compared with eikonal-based reaction model calculations combined with shell-model overlap functions.Results: Owing to the remarkable selectivity of the one-neutron and two-proton knockout reactions, a significantly updated level scheme for 32 Mg, which exhibits negative-parity intruder and positive-parity normal states, was constructed. The experimental results were confronted with four different nuclear structure models. Conclusions:In some of these models, different aspects of 32 Mg and the transition into the island of inversion are well described. However, unexplained discrepancies remain, and even with the help of these state-of-the-art theoretical approaches, the structure of this key nucleus is not yet fully captured.

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“…The breakdown of the canonical magic numbers in unstable nuclei has attracted much attention over the years [1,2]. To date, the disappearance of magicity has been reported in several regions of the nuclear chart away from the stability line.…”

Section: Introductionmentioning

confidence: 99%

In-beam $γ$-ray spectroscopy of $^{32}$Mg via direct reactions

Kitamura,

Wimmer,

Miyagi

et al. 2022

Preprint

0

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Background: The nucleus 32 Mg (N = 20 and Z = 12) plays a central role in the so-called "island of inversion" where in the ground states sd-shell neutrons are promoted to the f p-shell orbitals across the shell gap, resulting in the disappearance of the canonical neutron magic number N = 20.Purpose: The primary goals of this work are to extend the level scheme of 32 Mg, provide spin-parity assignments to excited states, and discuss the microscopic structure of each state through comparisons with theoretical calculations.Method: In-beam γ-ray spectroscopy of 32 Mg was performed using two direct-reaction probes, one-neutron (twoproton) knockout reactions on 33 Mg ( 34 Si). Final-state exclusive cross sections and parallel momentum distributions were extracted from the experimental data and compared with eikonal-based reaction model calculations combined with shell-model overlap functions.Results: Owing to the remarkable selectivity of the one-neutron and two-proton knockout reactions, a significantly updated level scheme for 32 Mg, which exhibits negative-parity intruder and positive-parity normal states, was constructed. The experimental results were confronted with four different nuclear structure models. Conclusions:In some of these models, different aspects of 32 Mg and the transition into the island of inversion are well described. However, unexplained discrepancies remain, and even with the help of these state-of-the-art theoretical approaches, the structure of this key nucleus is not yet fully captured.

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“…Beyond N=28, the N=40 region has gathered much interest in the last decade as a possible IOI site with signs of strong collective behavior and shape deformation [10,11,12,13,14,15,16,17]. Some measurements suggest the collective behavior to persist even past N=40 isotones [18,19], and with largescale shell-model calculations predicting even an extension to a fifth IOI [20,21]. Since such an IOI is currently beyond reach of experiment, this prediction should be checked by other theoretical approaches.…”

Section: Introductionmentioning

confidence: 99%

Summit of the N=40 Island of Inversion: precision mass measurements and ab initio calculations of neutron-rich chromium isotopes

Silwal,

Andreoiu,

Ashrafkhani

et al. 2022

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0

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Mass measurements continue to provide invaluable information for elucidating nuclear structure and scenarios of astrophysical interest. The transition region between the Z = 20 and 28 proton shell closures is particularly interesting due to the onset and evolution of nuclear deformation as nuclei become more neutron rich. This provides a critical testing ground for emerging ab-initio nuclear structure models. Here, we present high-precision mass measurements of neutron-rich chromium isotopes using the sensitive electrostatic Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) at TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) facility. Our high-precision mass measurements of 59,61−63 Cr confirm previous results, and the improved precision in measurements of 64−65 Cr refine the mass surface beyond N=40. With the ab initio in-medium similarity renormalization group, we examine the trends in collectivity in chromium isotopes and give a complete picture of the N=40 island of inversion from calcium to nickel.

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The neutron-rich edge of the nuclear landscape: Experiment and theory.

Cited by 63 publications

References 327 publications

In-beam γ -ray spectroscopy of Mg32 via direct reactions

In-beam γ -ray spectroscopy of Mg32 via direct reactions

In-beam $γ$-ray spectroscopy of $^{32}$Mg via direct reactions

Summit of the N=40 Island of Inversion: precision mass measurements and ab initio calculations of neutron-rich chromium isotopes

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