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Joakim

Joakim Cederkäll

Professor

Joakim

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

Author

  • M. Vandebrouck
  • A. Lepailleur
  • O. Sorlin
  • T. Aumann
  • C. Caesar
  • M. Holl
  • V. Panin
  • F. Wamers
  • S. R. Stroberg
  • J. D. Holt
  • F. De Oliveira 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. Caamaño
  • E. Casarejos
  • W. Catford
  • J. Cederkäll
  • M. Chartier
  • L. Chulkov
  • D. Cortina-Gil
  • E. Cravo
  • R. Crespo
  • U. Datta Pramanik
  • P. Díaz Fernández
  • I. Dillmann
  • Z. Elekes
  • J. Enders
  • O. Ershova
  • A. Estradé
  • F. Farinon
  • L. M. Fraile
  • M. Freer
  • D. Galaviz
  • H. Geissel
  • R. Gernhäuser
  • J. Gibelin
  • P. Golubev
  • K. Göbel
  • J. Hagdahl
  • A. Knyazev
  • J. T. Taylor
Show all

Summary, in English

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.

Department/s

  • Nuclear physics

Publishing year

2017-11-08

Language

English

Publication/Series

Physical Review C

Volume

96

Issue

5

Document type

Journal article

Publisher

American Physical Society

Topic

  • Subatomic Physics

Status

Published

ISBN/ISSN/Other

  • ISSN: 2469-9985