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

M. Vandebrouck ; A. Lepailleur ; O. Sorlin ; T. Aumann ; C. Caesar ; M. Holl ; V. Panin ; F. Wamers ; S. R. Stroberg ; J. D. Holt ; F. D. O. Santos ; H. Alvarez-Pol ; L. Atar ; V. Avdeichikov ; S. Beceiro-Novo ; D. Bemmerer ; J. Benlliure ; C. A. Bertulani ; S. K. Bogner ; J. M. Boillos ; K. Boretzky ; M. J. G. Borge ; M. Caamano ; E. Casarejos ; W. Catford ; J. Cederkall ; M. Chartier ; L. Chulkov ; D. Cortina-Gil ; E. Cravo ; R. Crespo ; U. D. Pramanik ; P. D. Fernandez ; I. Dillmann ; Z. Elekes ; J. Enders ; O. Ershova ; A. Estrade ; F. Farinon ; L. M. Fraile ; M. Freer ; D. Galaviz ; H. Geissel ; R. Gernhauser ; J. Gibelin ; P. Golubev ; K. Gobel ; Julius Hagdahl (Institutionen för fysik (Chalmers)) ; T. Heftrich ; M. Heil ; M. Heine ; Andreas Martin Heinz (Institutionen för fysik, Subatomär fysik och plasmafysik (Chalmers)) ; A. Henriques ; H. Hergert ; A. Hufnagel ; A. Ignatov ; Håkan T. Johansson (Institutionen för fysik, Subatomär fysik och plasmafysik (Chalmers)) ; Björn Jonson (Institutionen för fysik, Subatomär fysik och plasmafysik (Chalmers)) ; J. Kahlbow ; N. Kalantar-Nayestanaki ; R. Kanungo ; A. Kelic-Heil ; A. Knyazev ; T. Kroll ; N. Kurz ; M. Labiche ; C. Langer ; T. Le Bleis ; R. Lemmon ; Simon Lindberg (Institutionen för fysik, Subatomär fysik och plasmafysik (Chalmers)) ; J. Machado ; J. Marganiec ; F. M. Marques ; A. Movsesyan ; E. Nacher ; M. Najafi ; E. Nikolskii ; Thomas Nilsson (Institutionen för fysik (Chalmers)) ; C. Nociforo ; S. Paschalis ; A. Perea ; M. Petri ; S. Pietri ; R. Plag ; R. Reifarth ; G. Ribeiro ; C. Rigollet ; M. Roder ; D. Rossi ; D. Savran ; H. Scheit ; A. Schwenk ; H. Simon ; I. Syndikus ; J. T. Taylor ; O. Tengblad ; Ronja Thies (Institutionen för fysik, Subatomär fysik och plasmafysik (Chalmers)) ; Y. Togano ; P. Velho ; V. Volkov ; A. Wagner ; H. Weick ; C. Wheldon ; G. Wilson ; J. S. Winfield ; P. Woods ; D. Yakorev ; Mikhail V. Zhukov (Institutionen för fysik, Subatomär fysik och plasmafysik (Chalmers)) ; A. Zilges ; K. Zuber
Physical Review C (2469-9985). Vol. 96 (2017), 5,
[Artikel, refereegranskad vetenskaplig]

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 F-26 nucleus, composed of a deeply bound pi 0d(5/2) proton and an unbound v0d(3/2) neutron on top of an O-24 core, is particularly adapted for this purpose. The coupling of this proton and neutron results in a J(pi) = 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(pi) = 1(1)(+), 2(1)(+), 4(1)(+) bound states have been determined, and only a clear identification of the J(pi) = 3(1)(+) is missing. Purpose: We wish to complete the study of the J(pi) = 1(1)(+) - 4(1)(+) multiplet in F-26, by studying the energy and width of the J(pi) = 3(1)(+) unbound state. The method was first validated by the study of unbound states in F-25, for which resonances were already observed in a previous experiment. Method: Radioactive beams of Ne-26 and Ne-27, produced at about 440AMeV by the fragment separator at the GSI facility were used to populate unbound states in F-25 and F-26 via one-proton knockout reactions on a CH2 target, located at the object focal point of the (RB)-B-3/LAND setup. The detection of emitted. 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 F-25 and two in F-26. Results: Based on its width and decay properties, the first unbound state in F-25, at the relative energy of 49(9) keV, is proposed to be a J(pi) = 1/ 2(-) arising from a p1/2 proton- hole state. In F-26, the first resonance at 323(33) keV is proposed to be the J(pi) = 3(1)(+) member of the J(pi) = 1(1)(+) - 4(1)(+) multiplet. Energies of observed states in F-25,F-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 F-26.



Denna post skapades 2017-11-27. Senast ändrad 2017-11-27.
CPL Pubid: 253396

 

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