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Author(s)
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Jonson, B (Chalmers U. Tech. ; CERN) ; Schrieder, G (Darmstadt, Tech. U.) ; Cortina-Gil, D (Darmstadt, GSI ; Univ Santiago de Compostela, Santiago De Compostela 15706, Spain.) ; Simon, H (Darmstadt, GSI) ; Emling, H (Darmstadt, GSI) ; Nyman, G (Chalmers U. Tech.) ; Nilsson, T (Chalmers U. Tech. ; Darmstadt, Tech. U.) ; Johansson, H T (Chalmers U. Tech.) ; Borge, M J G (Madrid, Inst. Estructura Materia) ; Paschalis, S (Liverpool U.) ; Muenzenberg, G (Darmstadt, GSI) ; Zhukov, M V (Chalmers U. Tech.) ; Weick, H (Darmstadt, GSI) ; Pramanik, U Datta (Saha Inst.) ; LeBleis, T (Darmstadt, GSI) ; Meister, M (Chalmers U. Tech.) ; Reifarth, R (Darmstadt, GSI ; Frankfurt U., Inst. Kernphys.) ; Chulkov, L V (Darmstadt, GSI ; Kurchatov Inst., Moscow) ; Lantz, M (Chalmers U. Tech.) ; Riisager, K (Aarhus U.) ; Mahata, K (Darmstadt, GSI) ; Suemmerer, K (Darmstadt, GSI) ; Langer, C (Darmstadt, GSI) ; Chatillon, A (Darmstadt, GSI) ; Richter, A (Darmstadt, Tech. U. ; ECT, Trento) ; Kulessa, R (Jagiellonian U. (main)) ; Palit, R (Frankfurt U., Inst. Kernphys.) ; Aksyutina, Yu (Chalmers U. Tech. ; Darmstadt, GSI) ; Geissel, H (Darmstadt, GSI) ; Aumann, T (Darmstadt, GSI) ; Prokopowicz, W (Darmstadt, GSI) ; Forssen, C (Chalmers U. Tech.) ; Ickert, G (Darmstadt, GSI) ; Fynbo, H O U (Aarhus U.) ; Tengblad, O (Madrid, Inst. Estructura Materia) ; Boretzky, K (Darmstadt, GSI) |
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Abstract
| The unbound nuclei He-9 and He-10 have been produced in proton-knockout reactions from a 280 MeV/u Li-11 beam impinging on a liquid hydrogen target at the ALADIN-LAND setup at GSI. Information on their nuclear structure has been obtained from the relative-energy spectra, He-8 + n and He-8 + 2n, employing reaction models incorporating the structure of Li-11. The (8H)e + n relative-energy spectrum is dominated by a strong peak-like structure at low energy, which may be interpreted within the effective-range approximation as the result of an s-wave interaction with a neutron scattering length of -3.17(66) fm. This spectrum also shows evidence for resonance states at 1.33(8) MeV and at 2.4 MeV above the He-8 + n threshold. It is argued that the s-state might not be the He-9 ground state. For He-8 + n + n, the analysis of the relative-energy spectrum gives two alternative possibilities for an interpretation: either a narrow resonance at 1.42(10) MeV (Gamma = 1.11(76) MeV) superimposed on a correlated background, or two overlapping resonances, a ground state at 1.54(11) MeV (Gamma = 1.91(41) MeV) together with an excited state at 3.99(26) MeV (Gamma = 1.64(89) MeV). The two possible interpretations are discussed. (C) 2010 Elsevier B.V. All rights reserved. |