Direct evidence for the onset of intruder configurations in neutron-rich Ne isotopes

Terry, J. R.; Bazin, D.; Brown, B. A.; Campbell, C. M.; Church, Jennifer; Cook, J. M.; Davies, A. D.; Dinca, D. C.; Enders, J.; Gade, A.; Glasmacher, T.; Hansen, P. G.; Lecouey, J. L.; Otsuka, T.; Pritychenko, B.; Sherrill, B. M.; Tostevin, J. A.; Utsuno, Yutaka; Yoneda, K.; Zwahlen, Helmut T.

doi:10.1016/j.physletb.2006.06.061

Cited by 73 publications

(59 citation statements)

References 36 publications

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“…A shell-model interpretation suggests that the interaction between coexisting normal and intruder configurations significantly perturbs the energy of the 2 + 1 state in 28 Ne, thus producing large quadrupole deformation. Reaction studies on 28 Ne (see, e.g., [48,49]) are also consistent with the presence of fp-shell configurations at low excitation energy, meaning that for Z = 10 the neutron sd-fp shell gap starts to vanish already at N = 18. This can also explain the observed increase in the mean square charge radius toward 28 Ne.…”

Section: Even-even Neon Isotopesmentioning

confidence: 69%

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 Isotopesmentioning

confidence: 69%

Charge radii of neon isotopes across thesdneutron shell

et al. 2011

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“…First employed to study halo systems [8][9][10], subsequent analyses have used this experimental approach to deduce spectroscopic factors of individual single-particle states in many cases [5,[11][12][13][14][15][16]. In so doing, nucleon knockout reactions have contributed to the clarification of the evolution of shell structure toward the nucleon drip lines, helping to unravel the disappearance of familiar magic numbers and the formation of new shell gaps in nuclei with extreme N : Z ratios [17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Reduction of spectroscopic strength: Weakly-bound and strongly-bound single-particle states studied using one-nucleon knockout reactions

et al. 2008

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Both one-proton and one-neutron knockout reactions were performed with fast beams of two asymmetric, neutron-deficient rare isotopes produced by projectile fragmentation. The reactions are used to probe the nucleon spectroscopic strengths at both the weakly and strongly bound nucleon Fermi surfaces. The one-proton knockout reactions 9 Be( 28 S, 27 P)X and 9 Be( 24 Si, 23 Al)X probe the weakly bound valence proton states and the one-neutron knockout reactions and 9 Be( 28 S, 27 S)X and 9 Be( 24 Si, 23 Si)X the strongly bound neutron states in the two systems. The spectroscopic strengths are extracted from the measured cross sections by comparisons with an eikonal reaction theory. The reduction of the experimentally deduced spectroscopic strengths, relative to the predictions of shell-model calculations, is of order 0.8-0.9 in the removal of weakly bound protons and 0.3-0.4 in the knockout of the strongly bound neutrons. These results support previous studies at the extremes of nuclear binding and provide further evidence that in asymmetric nuclear systems the nucleons of the deficient species, at the more-bound Fermi surface are more strongly correlated than those of the more weakly bound excess species.

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“…Analyses have been used to deduce quantitative singleparticle spectroscopy in many instances, e.g., [3][4][5][6], and contributed to our understanding of the evolution of shell structures in nuclei with the most extreme N:Z ratios. Recent examples include [7][8][9][10].We consider analogous two-nucleon removal reactions, events in which intermediate-energy, mass A projectiles undergo grazing collisions with a light nuclear target, resulting in the sudden removal of two like nucleons. The reactions of interest involve the removal of two protons from neutron-rich and two neutrons from neutron-deficient projectiles.…”

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confidence: 99%

Two-Nucleon Knockout Spectroscopy at the Limits of Nuclear Stability

et al. 2009

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Sudden single-nucleon removal reactions from fast radioactive beams are now key to studies of the structure of rare isotopes. The sensitivity of the heavy residue's parallel momentum distribution to the orbital angular momentum of the removed nucleon is a crucial feature with a high spectroscopic value. Twonucleon removal reactions provide experimental reach toward the rarest nuclear species. We show that the residue parallel momentum distributions in these reactions offer a clear spectroscopic signal of the angular momentum of the pair of nucleons removed, and thus of the residue final state spins and spectroscopy. Our formalism is applied successfully to new final-state-inclusive measurements of like-nucleon pair removal reactions to states in neutron-rich 36 Mg and neutron-deficient 20 Mg. We also confront a new final-stateexclusive decomposition of two-proton knockout data to states in neutron-rich 26 Ne. DOI: 10.1103/PhysRevLett.102.132502 PACS numbers: 23.20.Lv, 21.60.Cs, 24.50.+g, 27.30.+t Intermediate-energy one-nucleon knockout reactions from rare-isotope beams are now key to our obtaining spectroscopic information on the dominant proton and neutron single-particle structures near the Fermi surfaces of short-lived isotopes far from the valley of stability [1,2]. The potency of the method, aside from its high experimental efficiency, is the combination of measurements of cross sections and their distribution with the parallel momentum of the projectilelike residues that derive information on the spectroscopic strength and orbital angular momentum of the removed nucleon, respectively. Analyses have been used to deduce quantitative singleparticle spectroscopy in many instances, e.g., [3][4][5][6], and contributed to our understanding of the evolution of shell structures in nuclei with the most extreme N:Z ratios. Recent examples include [7][8][9][10].We consider analogous two-nucleon removal reactions, events in which intermediate-energy, mass A projectiles undergo grazing collisions with a light nuclear target, resulting in the sudden removal of two like nucleons. The reactions of interest involve the removal of two protons from neutron-rich and two neutrons from neutron-deficient projectiles. In both cases the removed nucleons are strongly bound. We describe measurements where only the mass A À 2 projectile residues (denoted c) are detected. Ideally, the energy of the final states of the residues are also identified by measurement of their in-flight decay rays. Key to physical interpretation is that, in the sudden approximation, the sum,~1 þ~2, of the momenta of the removed nucleons in the projectile rest frame is probed by the laboratory momenta of the projectileK A and the residueK c measured in two-nucleon removal events,~1shown schematically in Fig. 1. Experiments determine the residue momentum component relative to a single direction. While early work on halo nuclei [11] looked at the component transverse to the beam direction, the distributions with respect to the parallel component are now pre...

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Direct evidence for the onset of intruder configurations in neutron-rich Ne isotopes

Cited by 73 publications

References 36 publications

Charge radii of neon isotopes across thesdneutron shell

Charge radii of neon isotopes across thesdneutron shell

Reduction of spectroscopic strength: Weakly-bound and strongly-bound single-particle states studied using one-nucleon knockout reactions

Two-Nucleon Knockout Spectroscopy at the Limits of Nuclear Stability

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