Role of intruder configurations in Ne and Mg

Pritychenko, B.; Glasmacher, T.; Cottle, P. D.; Fauerbach, M.; Ibbotson, R. W.; Kemper, K. W.; Maddalena, V.; Navin, A.; Ronningen, R. M.; Sakharuk, Alexander; Scheit, H.; Zelevinsky, Vladimir

doi:10.1016/s0370-2693(99)00850-3

Cited by 174 publications

(244 citation statements)

References 28 publications

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“…For 26 Ne and 28 Ne the excitation energies and B(E2) values of the lowest J π = 2 + state were first measured [35] 26 Ne is consistent with the sd-shell model description [43,45] which predicts that E(2 + 1 ) remains almost constant for N = 16-20. However, for 28 Ne the experimental value of E(2 + 1 ) drops considerably and is in good agreement with calculations in an extended sd-fp model space [46].…”

Section: Even-even Neon Isotopessupporting

confidence: 58%

Charge radii of neon isotopes across thesdneutron shell

et al. 2011

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We report on the changes in mean square charge radii of unstable neon nuclei relative to the stable 20 Ne, based on the measurement of optical isotope shifts. The studies were carried out using collinear laser spectroscopy on a fast beam of neutral neon atoms. High sensitivity on short-lived isotopes was achieved thanks to nonoptical detection based on optical pumping and state-selective collisional ionization, which was complemented by an accurate determination of the beam kinetic energy. The new results provide information on the structural changes in the sequence of neon isotopes all across the neutron sd shell, ranging from the proton drip line nucleus and halo candidate 17 Ne up to the neutron-rich 28 Ne in the vicinity of the "island of inversion." Within this range the charge radius is smallest for 24 Ne with N = 14 corresponding to the closure of the neutron d 5/2 shell, while it increases toward both neutron shell closures, N = 8 and N = 20. The general trend of the charge radii correlates well with the deformation effects which are known to be large for several neon isotopes. In the neutron-deficient isotopes, structural changes arise from the onset of proton-halo formation for 17 Ne, shell closure in 18 Ne, and clustering effects in 20,21 Ne. On the neutron-rich side the transition to the island of inversion plays an important role, with the radii in the upper part of the sd shell confirming the weakening of the N = 20 magic number. The results add new information to the radii systematics of light nuclei where data are scarce because of the small contribution of nuclear-size effects to the isotope shifts which are dominated by the finite-mass effect.

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Section: Even-even Neon Isotopessupporting

confidence: 58%

Charge radii of neon isotopes across thesdneutron shell

et al. 2011

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“…Neutron-knockout experiments performed in the region [11] are also a powerful tool to deduce the single-particle occupancies in the ground state of these nuclei, showing the dominance of the 0hω configurations in 30 Mg. These suggest that the transition to the "island of inversion" happens at 31 Mg and are corroborated by the Coulomb excitation data [3,4]. Recent results in 36 Mg [12] also indicate characteristics associated with intruder configurations suggesting that the size of the island of inversion is larger than originally anticipated [7].…”

Section: Introductionsupporting

confidence: 63%

“…Since the γ -ray of interest is emitted promptly (picoseconds) after the direct reaction feeding the state, there are no significant effects which de-align the nuclear spin. Furthermore, higher orders of alignment were calculated to be negligible, i.e., B 4 B 2 . Calculations were also performed for higher lying 0hω states predicted within the shell model, including the 5/2 + 1 state which also has a significant feeding in the reaction.…”

Section: Spin Alignment Calculation and Angular Distributionmentioning

confidence: 99%

“…For the isotopes in the "island of inversion," configurations with neutrons excited across the shell gap become energetically more favorable than the 0hω states which have no excitations into the fp-shell [1]. This suggests a breakdown in the N = 20 magic number as shown by the small 2 + 1 energy in 32 Mg [2] and a large B(E2) [3,4] for the transition to the ground state. Investigation of these nuclei are an important test of the mechanisms that drive the changes in single-particle structure.…”

Section: Introductionmentioning

confidence: 99%

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Intermediate energy proton knockout to the “island of inversion” isotopeMg31

et al. 2009

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The "island of the inversion" isotope 31 Mg was investigated using an intermediate energy proton knockout reaction from 32 Al at 90 MeV/nucleon at the National Superconducting Cyclotron Laboratory. A negligible cross section to the ground state supports an intruder-dominant configuration in 31 Mg. The partial cross sections to excited final states preferentially populate configurations in the 31 Mg residues which have no neutron excitations across the N = 20 shell closure. There is strong evidence that the reaction populates the 3/2 + and 5/2 + states which correspond with the neutron-hole states predicted by the shell model with the model space truncated above the sd-shell.

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“…Much effort has been devoted since then to the study of level schemes in attempting to understand this. The large B(E2) values deduced from the Coulomb excitation * ritu@triumf.ca measurements [3,4] were suggestive of 32 Mg being a deformed nucleus. It should be noted here that the extraction of the deformation value (β) in [3] is obtained under the assumption of a collective model.…”

mentioning

confidence: 97%

Matter radii of32−35Mg

Kanungo¹,

Procházka²,

Horiuchi³

et al. 2011

Phys. Rev. C

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The interaction cross sections of [32][33][34][35] Mg at 900A MeV have been measurmed using the fragment separator at GSI. The deviation from the r 0 A 1/3 trend is slightly larger for 35 Mg, signaling the possible formation of a longer tail in the neutron distribution for 35 Mg. The radii extracted from a Glauber model analysis with Fermi densities are consistent with models predicting the development of neutron skins. The shell structure of nuclei has formed a fundamental basis for understanding their properties. As nuclei accumulate a large excess of neutrons, the conventional shell structure starts to show signs of mutation. Investigations of ground-state properties of neutron-rich nuclei are a key toward the search for the effects leading to the breakdown of the conventional shell structure. The matter radii of neutron-rich nuclei are one of the fundamental properties that constrain nuclear wave functions and carry crucial information on deformation, shell effects, and formation of neutron skins and halos [1].In this Rapid Communication we report on the first determination of the matter radii of [33][34][35] Mg in the N = 20 island of inversion from a measurement of the interaction cross section. The results are consistent with development of neutron skins with 35 Mg showing the possibility of a longer density tail.The breakdown of the N = 20 shell gap was observed through the low excitation energy of the 2 + state in 32 Mg [2]. Much effort has been devoted since then to the study of level schemes in attempting to understand this. The large B(E2) values deduced from the Coulomb excitation * ritu@triumf.ca measurements [3,4] were suggestive of 32 Mg being a deformed nucleus. It should be noted here that the extraction of the deformation value (β) in [3] is obtained under the assumption of a collective model. For a proper understanding of deformation in these nuclei, measured radii are important.The level scheme of 32 Mg from β delayed γ spectroscopy of 32 Na [5] suggests that 32 Mg is not an axially symmetric rotor. It is not a vibrational nucleus either. It was in fact discussed [6], based on a Skyrme-Hartree-Fock description, that this nucleus probably exhibits γ unstable deformation. A relativistic mean-field (RMF) calculation with three-dimensional angular momentum projection involving triaxial degrees of freedom [7] gives a ground state having β = 0.6 and γ = 10 • . Density and radii from such models would be useful for comparison with the present data. Recently, a shape coexistent 0 + state has been found in 32 Mg [8].The Monte Carlo shell model (MCSM) [9] has been considered to be fairly well suited to describe the levels in nuclei around the island of inversion. The predicted level scheme of 32 Mg also does not show features of an axially symmetric rotor.Mean-field models based on the Hartree-Fock (HF) or Hartree-Fock-Bogoliubov (HFB) approximations have been developed by several groups [10][11][12] for the neutron-rich 021302-1 0556-2813/2011/83(2)/021302(4)

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Role of intruder configurations in Ne and Mg

Cited by 174 publications

References 28 publications

Charge radii of neon isotopes across thesdneutron shell

Charge radii of neon isotopes across thesdneutron shell

Intermediate energy proton knockout to the “island of inversion” isotopeMg31

Matter radii of32−35Mg

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