# Beyond the neutron drip line: The unbound oxygen isotopes $^{25}$O and $^{26}$O

Abstract : The very neutron-rich oxygen isotopes 25O and 26O are investigated experimentally and theoretically. The unbound states are populated in an experiment performed at the R3B-LAND setup at GSI via proton-knockout reactions from 26F and 27F at relativistic energies around 442 and 414 MeV/nucleon, respectively. From the kinematically complete measurement of the decay into 24O plus one or two neutrons, the 25O ground-state energy and width are determined, and upper limits for the 26O ground-state energy and lifetime are extracted. In addition, the results provide indications for an excited state in 26O at around 4MeV. The experimental findings are compared to theoretical shell-model calculations based on chiral two- and three-nucleon (3N) forces, including for the first time residual 3N forces, which are shown to be amplified as valence neutrons are added.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-00862732
Contributor : Michel Lion <>
Submitted on : Tuesday, September 17, 2013 - 1:53:09 PM
Last modification on : Tuesday, December 1, 2020 - 4:10:04 PM

### Citation

C. Caesar, J. Simonis, T. Adachi, Y. Aksyutina, J. Alcantara, et al.. Beyond the neutron drip line: The unbound oxygen isotopes $^{25}$O and $^{26}$O. Physical Review C, American Physical Society, 2013, 88, pp.034313. ⟨10.1103/PhysRevC.88.034313⟩. ⟨in2p3-00862732⟩

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