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Effective proton-neutron interaction near the drip line from unbound states in F 25,26

Vandebrouck, M.; Lepailleur, A.; Sorlin, O.; Aumann, T.; Caesar, C.; Holl, M.; Panin, V.; Wamers, F.; Stroberg, S. R. and Holt, J. D., et al. (2017) In Physical Review C 96(5).
Abstract

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 F26 nucleus, composed of a deeply bound π0d5/2 proton and an unbound ν0d3/2 neutron on top of an O24 core, is particularly adapted for this purpose. The coupling of this proton and neutron results in a Jπ=11+-41+ multiplet, whose energies must be determined to study the influence of the proximity of the continuum on the corresponding proton-neutron interaction. The Jπ=11+,21+,41+ bound states have been determined, and only a clear identification of the Jπ=31+ is missing.... (More)

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 F26 nucleus, composed of a deeply bound π0d5/2 proton and an unbound ν0d3/2 neutron on top of an O24 core, is particularly adapted for this purpose. The coupling of this proton and neutron results in a Jπ=11+-41+ multiplet, whose energies must be determined to study the influence of the proximity of the continuum on the corresponding proton-neutron interaction. The Jπ=11+,21+,41+ bound states have been determined, and only a clear identification of the Jπ=31+ is missing. Purpose: We wish to complete the study of the Jπ=11+-41+ multiplet in F26, by studying the energy and width of the Jπ=31+ unbound state. The method was first validated by the study of unbound states in F25, for which resonances were already observed in a previous experiment. Method: Radioactive beams of Ne26 and Ne27, produced at about 440AMeV by the fragment separator at the GSI facility were used to populate unbound states in F25 and F26 via one-proton knockout reactions on a CH2 target, located at the object focal point of the R3B/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 F25 and two in F26. Results: Based on its width and decay properties, the first unbound state in F25, at the relative energy of 49(9) keV, is proposed to be a Jπ=1/2- arising from a p1/2 proton-hole state. In F26, the first resonance at 323(33) keV is proposed to be the Jπ=31+ member of the Jπ=11+-41+ multiplet. Energies of observed states in F25,26 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 F26.

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Physical Review C
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96
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5
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American Physical Society
external identifiers
  • scopus:85033794918
  • wos:000414668700001
ISSN
2469-9985
DOI
10.1103/PhysRevC.96.054305
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English
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3cf1917a-eba6-434d-aae8-014cf529f7df
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2017-11-29 09:41:21
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2018-04-08 05:02:32
@article{3cf1917a-eba6-434d-aae8-014cf529f7df,
  abstract     = {<p>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 F26 nucleus, composed of a deeply bound π0d5/2 proton and an unbound ν0d3/2 neutron on top of an O24 core, is particularly adapted for this purpose. The coupling of this proton and neutron results in a Jπ=11+-41+ multiplet, whose energies must be determined to study the influence of the proximity of the continuum on the corresponding proton-neutron interaction. The Jπ=11+,21+,41+ bound states have been determined, and only a clear identification of the Jπ=31+ is missing. Purpose: We wish to complete the study of the Jπ=11+-41+ multiplet in F26, by studying the energy and width of the Jπ=31+ unbound state. The method was first validated by the study of unbound states in F25, for which resonances were already observed in a previous experiment. Method: Radioactive beams of Ne26 and Ne27, produced at about 440AMeV by the fragment separator at the GSI facility were used to populate unbound states in F25 and F26 via one-proton knockout reactions on a CH2 target, located at the object focal point of the R3B/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 F25 and two in F26. Results: Based on its width and decay properties, the first unbound state in F25, at the relative energy of 49(9) keV, is proposed to be a Jπ=1/2- arising from a p1/2 proton-hole state. In F26, the first resonance at 323(33) keV is proposed to be the Jπ=31+ member of the Jπ=11+-41+ multiplet. Energies of observed states in F25,26 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 F26.</p>},
  articleno    = {054305},
  author       = {Vandebrouck, M. and Lepailleur, A. and Sorlin, O. and Aumann, T. and Caesar, C. and Holl, M. and Panin, V. and Wamers, F. and Stroberg, S. R. and Holt, J. D. and De Oliveira Santos, F. and Alvarez-Pol, H. and Atar, L. and Avdeichikov, V. and Beceiro-Novo, S. and Bemmerer, D. and Benlliure, J. and Bertulani, C. A. and Bogner, S. K. and Boillos, J. M. and Boretzky, K. and Borge, M. J.G. and Caamaño, M. and Casarejos, E. and Catford, W. and Cederkäll, J. and Chartier, M. and Chulkov, L. and Cortina-Gil, D. and Cravo, E. and Crespo, R. and Datta Pramanik, U. and Díaz Fernández, P. and Dillmann, I. and Elekes, Z. and Enders, J. and Ershova, O. and Estradé, A. and Farinon, F. and Fraile, L. M. and Freer, M. and Galaviz, D. and Geissel, H. and Gernhäuser, R. and Gibelin, J. and Golubev, P. and Göbel, K. and Hagdahl, J. and Heftrich, T. and Heil, M. and Heine, M. and Heinz, A. and Henriques, A. and Hergert, H. and Hufnagel, A. and Ignatov, A. and Johansson, H. T. and Jonson, B. and Kahlbow, J. and Kalantar-Nayestanaki, N. and Kanungo, R. and Kelic-Heil, A. and Knyazev, A. and Kröll, T. and Kurz, N. and Labiche, M. and Langer, C. and Le Bleis, T. and Lemmon, R. and Lindberg, S. and Machado, J. and Marganiec, J. and Marqués, F. M. and Movsesyan, A. and Nacher, E. and Najafi, M. and Nikolskii, E. and Nilsson, T. and Nociforo, C. and Paschalis, S. and Perea, A. and Petri, M. and Pietri, S. and Plag, R. and Reifarth, R. and Ribeiro, G. and Rigollet, C. and Röder, M. and Rossi, D. and Savran, D. and Scheit, H. and Schwenk, A. and Simon, H. and Syndikus, I. and Taylor, J. T. and Tengblad, O. and Thies, R. and Togano, Y. and Velho, P. and Volkov, V. and Wagner, A. and Weick, H. and Wheldon, C. and Wilson, G. and Winfield, J. S. and Woods, P. and Yakorev, D. and Zhukov, M. and Zilges, A. and Zuber, K. and , },
  issn         = {2469-9985},
  language     = {eng},
  month        = {11},
  number       = {5},
  publisher    = {American Physical Society},
  series       = {Physical Review C},
  title        = {Effective proton-neutron interaction near the drip line from unbound states in F 25,26},
  url          = {http://dx.doi.org/10.1103/PhysRevC.96.054305},
  volume       = {96},
  year         = {2017},
}