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Sökning: WFRF:(LeBleis T.)

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1.
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2.
  • Johansson, H. T., et al. (författare)
  • The unbound isotopes 9,10He
  • 2010
  • Ingår i: Nuclear Physics A. - Elsevier. - 0375-9474 .- 1873-1554. ; 842:1-4, s. 15-32
  • Tidskriftsartikel (refereegranskat)abstract
    • The unbound nuclei 9He and 10He have been produced in proton-knockout reactions from a 280 MeV/u 11Li 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, 8He + n and 8He + 2n, employing reaction models incorporating the structure of 11Li.
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3.
  • Johansson, H. T., et al. (författare)
  • Three-body correlations in the decay of He-10 and Li-13
  • 2010
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 847:1-2, s. 66-88
  • Tidskriftsartikel (refereegranskat)abstract
    • The very exotic nuclear resonance systems, 10He and 13Li, are produced in proton-knockout reactions from relativistic beams of 11Li and 14Be. The experimentally determined energy and angular correlations between their decay products, <img src="http://ars.els-cdn.com/content/image/1-s2.0-S0375947410006044-si1.gif" data-inlimgeid="1-s2.0-S0375947410006044-si1.gif" data-loaded="true" /> and <img src="http://ars.els-cdn.com/content/image/1-s2.0-S0375947410006044-si2.gif" data-inlimgeid="1-s2.0-S0375947410006044-si2.gif" data-loaded="true" />, are analyzed using an expansion of decay amplitudes in a restricted set of hyperspherical harmonics. By considering only a small number of terms it is possible to extract the expansion coefficients directly from the experimental three-body correlations. This provides a model-independent way of getting information about the decay process, on the structure of the decaying nucleus and on the quantum characteristics of the binary subsystems.The results show that the <img src="http://ars.els-cdn.com/content/image/1-s2.0-S0375947410006044-si3.gif" data-inlimgeid="1-s2.0-S0375947410006044-si3.gif" data-loaded="true" /> relative-energy spectrum can be interpreted as consisting of two resonances, an Iπ=0+ ground state and an excited Iπ=2+ state. The <img src="http://ars.els-cdn.com/content/image/1-s2.0-S0375947410006044-si6.gif" data-inlimgeid="1-s2.0-S0375947410006044-si6.gif" data-loaded="true" /> relative-energy spectrum is interpreted as an Iπ=3/2− ground state overlapping with excited states having a structure similar to the 2+ state in 10He but spread over several states due to the coupling to the Iπ=3/2− core. The13Li data also give evidence for a contribution of a configuration where the two neutrons occupy the d-shell.
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4.
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5.
  • Aksyutina, Y., et al. (författare)
  • Momentum profile analysis in one-neutron knockout from Borromean nuclei
  • 2013
  • Ingår i: Physics Letters B. - 0370-2693. ; 718:4-5, s. 1309-1313
  • Tidskriftsartikel (refereegranskat)abstract
    • One-neutron knockout reactions from Borromean nuclei are analyzed using a profile function analysis technique. The profile function, which is derived as the square root of the variance of the measured fragment + neutron momenta as a function of their relative energy, is shown to be very sensitive to the angular momentum of the knocked out neutron. Three cases are studied here: He-7, where the profile function analysis shows a presence of (s(1/2))(2) component in the He-8 ground-state wave-function, Li-10, where the presence of a 11(2)% d-wave contribution to the relative energy spectrum above 1.5 MeV is found and, finally, the presence of a major s contribution around 0.5 MeV relative energy in the Be-13 case and that the observed decay to the Be-12 2(+) state originates in a d state in Be-13.
6.
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7.
  • Aksyutina, Y., et al. (författare)
  • Structure of the unbound nucleus Be-13: One-neutron knockout reaction data from Be-14 analyzed in a holistic approach
  • 2013
  • Ingår i: Physical Review C. - 0556-2813. ; 87:6
  • Tidskriftsartikel (refereegranskat)abstract
    • At the ALADIN-LAND setup at GSI the unbound nucleus Be-13 has been produced in one-neutron knockout reactions from a 304 MeV/nucleon relativistic beam of Be-14 ions impinging on a liquid hydrogen target. An analysis of the data including all available information about Be-13, and in particular recent data from a similar experiment performed at RIKEN, has been performed. A consistent description is reached. It is found that the excitation spectrum is dominated by s-waves at low energy, which solves problems from previous seemingly contradictory interpretations. A possible interference between two s-states in Be-13 is also discussed. The results indicate that the ground-state wave function of Be-14 is dominated by valence neutrons in the s-shell contributing with 60-75% of the total neutron knockout cross section.
8.
  • Aksyutina, Y., et al. (författare)
  • Study of the Be14 continuum: Identification and structure of its second 2+ state
  • 2013
  • Ingår i: Physical Review Letters. - 0031-9007. ; 111:24
  • Tidskriftsartikel (refereegranskat)abstract
    • The coupling between bound quantum states and those in the continuum is of high theoretical interest. Experimental studies of bound drip-line nuclei provide ideal testing grounds for such investigations since they, due to the feeble binding energy of their valence particles, are easy to excite into the continuum. In this Letter, continuum states in the heaviest particle-stable Be isotope, Be14, are studied by employing the method of inelastic proton scattering in inverse kinematics. New continuum states are found at excitation energies E*=3.54(16) MeV and E*=5.25(19) MeV. The structure of the earlier known 21+ state at 1.54(13) MeV was confirmed with a predominantly (0d5/2)2 configuration while there is very clear evidence that the 22+ state has a predominant (1s1/2, 0d 5/2) structure with a preferential three-body decay mechanism. The region at about 7 MeV excitation shows distinct features of sequential neutron decay via intermediate states in Be13. This demonstrates that the increasing availability of energetic beams of exotic nuclei opens up new vistas for experiments leading towards a new understanding of the interplay between bound and continuum states. © 2013 American Physical Society.
9.
  • Johansson, Håkan T., 1977-, et al. (författare)
  • The unbound isotopes He-9,He-10
  • 2010
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 842, s. 15-32
  • Tidskriftsartikel (refereegranskat)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.
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