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Author(s)
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Marganiec, J ; Wamers, F ; Aksouh, F ; Aksyutina, Yu ; Alvarez-Pol, H ; Aumann, T ; Beceiro-Novo, S ; Boretzky, K ; Borge, M J G (CERN) ; Chartier, M ; Chatillon, A ; Chulkov, L V ; Cortina-Gil, D ; Emling, H ; Ershova, O ; Fraile, L M ; Fynbo, H O U ; Galaviz, D ; Geissel, H ; Heil, M ; Hoffmann, D H H ; Hoffmann, J ; Johansson, H T ; Jonson, B ; Karagiannis, C ; Kiselev, O A ; Kratz, J V ; Kulessa, R ; Kurz, N ; Langer, C ; Lantz, M ; Le Bleis, T ; Lemmon, R ; Litvinov, Yu A ; Mahata, K ; Müntz, C ; Nilsson, T ; Nociforo, C ; Nyman, G ; Ott, W ; Panin, V ; Paschalis, S ; Perea, A ; Plag, R ; Reifarth, R ; Richter, A ; Rodriguez-Tajes, C ; Rossi, D ; Riisager, K ; Savran, D ; Schrieder, G ; Simon, H ; Stroth, J ; Sümmerer, K ; Tengblad, O ; Weick, H ; Wiescher, M ; Wimmer, C ; Zhukov, M V |
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Abstract
| Two-proton decay of the unbound $ T_{z} =-2$ nucleus$^{16}$Ne , produced in one-neutron knockout from a 500 MeV/u$^{17}$Ne beam, has been studied at GSI. The ground state, at a resonance energy 1.388(15) MeV, ( $ \Gamma =0.082(15)$ MeV) above the$^{14}$O +p+p threshold, and two narrow resonances at $ E_{r} =3.220(46)$ MeV and 7.57(6) MeV have been investigated. A comparison of the energy difference between the first excited 2$^{+}$ state and the 0$^{+}$ ground state in$^{16}$Ne with its mirror nucleus$^{16}$C reveals a small Thomas-Ehrman shift (TES) of $ +70(46)$ keV. A trend of the TES for the T = 2 quintet is obtained by completing the known data with a prediction for$^{16}$F obtained from an IMME analysis. The decay mechanisms of the observed three resonances were revealed from an analysis of the energy and angular correlations of the$^{14}$O +p+p decay products. The ground state decay can be considered as a genuine three-body (democratic) mode and the excited states decay sequentially via states in the intermediate nucleus$^{15}$F , the 3.22 MeV state predominantly via the$^{15}$F ground-state resonance, while the 7.57 MeV state decays via the 5/2$^{+}$ resonance in$^{15}$F at 2.8 MeV above the$^{14}$O +p+p threshold. Further, from an analysis of angular correlations, the spin-parity of the 7.57 MeV state has been determined as $ I^{\pi} =2^{+}$ and assigned as the third 2$^{+}$ state in$^{16}$Ne based on a comparison with$^{16}$C. |