Aumann, T.

Chulkov, L.

Jonson, B.

Marganiec, J.

Nilsson, T.

Simon, H.

Wamers, F.

GSI Repository

Spin assignment of the 7.57 MeV state in the unbound nucleus 16Ne∗J. Marganiec1,2,3, F. Wamers1,2,3, T. Aumann1,3, L.V. Chulkov1,4, B. Jonson5, T. Nilsson5, H. Simon3,and the R3B collaboration1TU Darmstadt, Germany; 2EMMI, GSI Darmstadt, Germany; 3GSI Darmstadt, Germany; 4NRC Kurchatov Institute,Moscow, Russia; 5Chalmers Tekniska Ho¨gskola, Go¨teborg, SwedenTwo-proton decay of the unbound nucleus 16Ne, pro-duced in one-neutron knock-out from a 500 MeV/u 17Nebeam, has been studied at GSI. The beam was directed to-wards carbon (370 mg/cm2) or polyethylene (213 mg/cm2)targets. The reaction products were identified by means ofposition, energy loss, and Time-of-Flight measurements,using the R3B-LAND setup. Coincidences between 14Oand two protons provided the momentum four vectors,which were transformed into the projectile rest-mass frame,where two different sets of non-relativistic Jacobi coordi-nates (T - and Y -system) were used in the analysis [1].The internal kinetic energy (the relative energy) Efpp inthe three-body system 14O+p+p (see Fig. 1), and the frac-tional energies in the fragment-proton (ǫfp) and the proton-proton (ǫpp) subsystems were reconstructed. The correla-tion functions normalized to unity, for the fractional-energydistributions W (ǫfp) and W (ǫpp) and the angular distribu-tions W (cos θfp) and W (cos θpp), were constructed andanalyzed. The required efficiency and acceptance correc-tions have been estimated using the Monte Carlo simula-tions (see Ref. [2] for details).Figure 1: 14O+p+p relative energy spectrum.Correlations between the decay products from the ex-cited state at the resonance energy 7.57(6) MeV are shownin Fig. 2. The two peaks visible in W (ǫfp) and W (cos θpp)have been associated with transition to the state at Erel =2.8 MeV in 15F. The results of the calculations for the as-sumed initial spin value Ipi = 2+ and channel spin j = 5/2are shown in Fig. 2 as dashed lines. The physical back-ground contributions are shown in Fig. 2 as dotted lines.The sum of these two contributions (solid lines) perfectlyreproduces the experimental data (see Ref. [2] for details).∗Work supported by NAVI, GSI-TU Darmstadt cooperation, HIC forFAIR, EMMI and BMBF. (B.J.) is a Helmholtz International Fellow.Figure 2: Three-body correlations between the decay prod-ucts of the Erel = 7.57 MeV.In this case, the initial 2+ state emits a proton from thed5/2 shell feeding the 14O+p in a d5/2 shell configurationin 15F. This 2+ state is unstable and emits two protons. Itswidth is surprisingly narrow. This suggests that its structurecan be more complicated than a 14O+p+p state. This stateis also situated above the four proton emission threshold,what indicates a possible many-body structure. And the12C+4p configuration with four protons in the (sd) shell,could be the cause of such a narrow width of this state [3].A special case of such a structure could consist of an ex-cited core together with two protons, 14O(2+)+2p [4]. Thetheoretical predictions for the position of the second 2+state in 16Ne are E∗ = 4.2 MeV [5] or E∗ = 3.6 MeV [6],both close to the known position of the second 2+ state inthe mirror nucleus 16C [7]. From this mirror nucleus (thethird 2+ state of 16C is at E∗ = 6.11 MeV [8]), the inves-tigated state is assumed to be the third 2+ state in 16Ne.References[1] L.V. Grigorenko et al., Phys. Lett. B 677, 30 (2009)[2] J. Marganiec et al., Eur. Phys. J. A 51:9 (2015)[3] H.T. Fortune, R. Sherr, Phys. Rev. C 87, 057308 (2013)[4] I. Mukha et al., Phys. Rev. C 82, 054315 (2010)[5] N.K. Timofeyuk, P. Descouvemont, Phys. Rev. C 81, 051301(2010)[6] H.T. Fortune, R. Sherr, Phys. Rev. C 82, 027310 (2010)[7] M. Petri et al., Phys. Rev. C 86, 044329 (2012)[8] Y. Satou et al., Phys. Lett. B 728, 462 (2014)MU-NUSTAR-NR-02 GSI SCIENTIFIC REPORT 2014186 DOI:10.15120/GR-2015-1-MU-NUSTAR-NR-02

Spin assignment of the 7.57 MeV state in the unbound nucleus $^{16}$Ne

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Spin assignment of the 7.57 MeV state in the unbound nucleus $^{16}$ Ne

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Spin assignment of the 7.57 MeV state in the unbound nucleus 16^{16}16Ne

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Spin assignment of the 7.57 MeV state in the unbound nucleus $^{16}$ Ne