Publisher’s Note: One-neutron knockout from light neutron-rich nuclei at relativistic energies [Phys. Rev. C<b>82</b>, 024305 (2010)]

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One-neutron knockout data for 18−22 N are analyzed in the eikonal approximation of the Glauber model. The role of the s-d shell and the crossing of the N = 14 neutron subshell are discussed. Of particular interest is the nucleus 22 N, where the knockout data provide a sensitive experimental test for a possible halo structure of its ground state. The observation of a narrow momentum distribution of the 21 N fragments, together with an essential 1s 1/2 contribution needed to describe the observed longitudinal-momentum distribution, allow the firm conclusion that the ground state of 22 N is a well-developed nuclear halo. The results also show that the N = 14 subshell in 22 N is somewhat reduced as compared to that of 23 O.

“…Note that there are changes in the numerical values with respect to Ref. [5], since a more realistic Glauber-type model was adopted in this work.…”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure ofN22and theN=14subshell

Rodríguez–Tajes¹,

Cortina-Gil²,

Álvarez‐Pol³

et al. 2011

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“…The knockout of a 0d 5/2 proton from 27 Ne should leave the 26 F nucleus in the (π 0d 5/2 ) 1 (ν0d 3/2 ) 1 configuration and favor the 1 The structure of the ground state of 26 F was also investigated by the one-neutron-knockout reaction at relativistic energies [20]. The narrow inclusive momentum distribution of the 25 F residue pointed to the presence of valence neutrons in the 1s 1/2 state, in apparent contradiction with the neutron 0d 3/2 configuration of the 1 + ground state proposed above.…”

Section: Introductionmentioning

confidence: 99%

Effective proton-neutron interaction near the drip line from unbound states in F25,26

Vandebrouck¹,

Lepailleur²,

Sorlin³

et al. 2017

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Background: Odd-odd nuclei, around doubly closed shells, have been extensively used to study proton-neutron interactions. However, the evolution of these interactions as a function of the binding energy, ultimately when nuclei become unbound, is poorly known. The 26 F nucleus, composed of a deeply bound π 0d 5/2 proton and an unbound ν0d 3/2 neutron on top of an 24 O core, is particularly adapted for this purpose. The coupling of this proton and neutron results in a J π = 1 1 + − 4 1 + multiplet, whose energies must be determined to study the influence of the proximity of the continuum on the corresponding proton-neutron interaction. The J π = 1 1 + , 2 1 + , 4 1 + bound states have been determined, and only a clear identification of the J π = 3 1 + is missing. Purpose: We wish to complete the study of the J π = 1 1 + − 4 1 + multiplet in 26 F, by studying the energy and width of the J π = 3 1 + unbound state. The method was first validated by the study of unbound states in 25 F, for which resonances were already observed in a previous experiment. Method: Radioactive beams of 26 Ne and 27 Ne, produced at about 440A MeV by the fragment separator at the GSI facility were used to populate unbound states in 25 F and 26 F via one-proton knockout reactions on a CH 2 target, located at the object focal point of the R 3 B/LAND setup. The detection of emitted γ rays and neutrons, added to the reconstruction of the momentum vector of the A − 1 nuclei, allowed the determination of the energy of three unbound states in 25 F and two in 26 F. Results: Based on its width and decay properties, the first unbound state in 25 F, at the relative energy of 49(9) keV, is proposed to be a J π = 1/2 − arising from a p 1/2 proton-hole state. In 26 F, the first resonance at 323(33) keV is proposed to be the J π = 3 1 + member of the J π = 1 1 + − 4 1 + multiplet. Energies of observed states in 25,26 F have been compared to calculations using the independent-particle shell model, a phenomenological shell model, and the ab initio valence-space in-medium similarity renormalization group method. Conclusions: The deduced effective proton-neutron interaction is weakened by about 30-40% in comparison to the models, pointing to the need for implementing the role of the continuum in theoretical descriptions or to a wrong determination of the atomic mass of 26 F.

“…A one-neutron binding energy of 5.2 MeV can be interpreted as an enhanced pairing in a Hartree-Fock-Bogoliubov (HFB) calculation [29]. Recently, the inclusive measured cross section and momentum distribution of the fragment after one-neutron removal from 35 Al [28,29] showed occupancy of all orbitals (s, p, d, and f ) across the shell gap between sd and pf . But to understand more deeply the nucleon-nucleon interaction, it is important to explore details of the different components of the wave function, which is possible via exclusive measurements.…”

Section: Introductionmentioning

confidence: 99%

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

Chakraborty¹,

Pramanik²,

Aumann³

et al. 2017

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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.