Effective proton-neutron interaction near the drip line from unbound states in F-25,F-26
Journal article, 2017
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.
Author
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
Paloma Diaz 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
Chalmers, Physics
T. Heftrich
M. Heil
M. Heine
Andreas Martin Heinz
Chalmers, Physics, Subatomic and Plasma Physics
A. Henriques
H. Hergert
A. Hufnagel
A. Ignatov
Håkan T Johansson
Chalmers, Physics, Subatomic and Plasma Physics
Björn Jonson
Chalmers, Physics, Subatomic and Plasma Physics
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
Chalmers, Physics, Subatomic and Plasma Physics
J. Machado
J. Marganiec
F. M. Marques
A. Movsesyan
E. Nacher
M. Najafi
E. Nikolskii
Thomas Nilsson
Chalmers, Physics
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
Chalmers, Physics, Subatomic and Plasma Physics
Y. Togano
P. Velho
V. Volkov
A. Wagner
H. Weick
C. Wheldon
G. Wilson
J. S. Winfield
P. Woods
D. Yakorev
Mikhail Zhukov
Chalmers, Physics, Subatomic and Plasma Physics
A. Zilges
K. Zuber
Physical Review C
24699985 (ISSN) 24699993 (eISSN)
Vol. 96 5Subject Categories
Subatomic Physics
DOI
10.1103/PhysRevC.96.054305