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Träfflista för sökning "WFRF:(Jonson Björn) srt2:(2005-2009);pers:(Wilhelmsen Katarina 1962);pers:(Riisager K.);pers:(Fynbo H.O.U.)"

Sökning: WFRF:(Jonson Björn) > (2005-2009) > Wilhelmsen Katarina 1962 > Riisager K. > Fynbo H.O.U.

  • Resultat 1-8 av 8
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1.
  • Diget, C. A., et al. (författare)
  • Breakup channels for C-12 triple-alpha continuum states
  • 2009
  • Ingår i: Physical Review C. - 0556-2813. ; 80:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The triple-alpha-particle breakup of states in the triple-alpha continuum of C-12 has been investigated by way of coincident detection of all three alpha particles of the breakup. The states have been fed in the beta decay of N-12 and B-12, and the alpha particles measured using a setup that covers all of the triple-alpha phase space. Contributions from the breakup through the Be-8(0(+)) ground state as well as other channels-interpreted as breakup through excited energies in Be-8-have been identified. Spins and parities of C-12 triple-alpha continuum states are deduced from the measured phase-space distributions for breakup through Be-8 above the ground state by comparison to a fully symmetrized sequential R-matrix description of the breakup. At around 10 MeV in C-12, the breakup is found to be dominated by 0(+) strength breaking up through the ghost of the Be-8(0(+)) ground state with L = 0 angular momentum between the first emitted alpha particle and the intermediate Be-8 nucleus. For C-12 energies above the 12.7 MeV 1(+) state, however, L = 2 breakup of a C-12 2(+) state through the Be-8(2(+)) excited state dominates. Furthermore, the possibility of a 2(+) excited state in the 9-12 MeV region of C-12 is investigated.
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2.
  • Diget, C. A., et al. (författare)
  • Properties of the C-12 10 MeV state determined through beta-decay
  • 2005
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 760:1-2, s. 3
  • Tidskriftsartikel (refereegranskat)abstract
    • The beta-delayed triple-alpha particle decay of B-12 has been measured with a setup that favours coincidence detection. A broad state in C-12, previously reported around 10 MeV, has been seen and its properties determined through R-matrix analysis of the excitation spectrum. The spin and parity are 0(+). Interference between this state and the Hoyle state at 7.654 MeV has a marked influence on the spectrum. The coupling between the two states makes it difficult to determine the resonance energy. (c) 2005 Elsevier B.V. All rights reserved.
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3.
  • Fynbo, H. O. U., et al. (författare)
  • The β-decay approach for studying 12C
  • 2008
  • Ingår i: Journal of Physics: Conference Series. - 17426588. ; 111:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The β-decays of the mirror nuclei 12B and 12N both populate states in 12C and they are therefore a precious source of information about this nucleus. Due to the selection rules of β-decay only 0+, 1+ and 2+ states are populated. This allows a very clean study of unbound states just above the 3α-threshold with those spin and parities. This probe has been applied in two experiments using two complementary experimental techniques: in the first the three α-particles emitted after β-decay are measured in coincidence in separate detectors using the ISOL method, while in the second method 12B and 12N are implanted in a detector and the summed energy of the three α-particles is measured directly. Preliminary results from the two approaches are presented. © 2008 IOP Publishing Ltd.
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4.
  • Hyldegaard, S., et al. (författare)
  • Branching ratios in the beta decays of N-12 and B-12
  • 2009
  • Ingår i: Physical Review C. - 0556-2813. ; 80:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Absolute branching ratios to unbound states in C-12 populated in the beta decays of N-12 and B-12 are reported. Clean sources of N-12 and B-12 were obtained using the isotope separation on-line (ISOL) method. The relative branching ratios to the different populated states were extracted using single-alpha as well as complete kinematics triple-alpha spectra. These two largely independent methods give consistent results. Absolute normalization is achieved via the precisely known absolute branching ratio to the bound 4.44 MeV state in C-12. The extracted branching ratios to the unbound states are a factor of three more precise than previous measurements. Branching ratios in the decay of Na-20 are also extracted and used to check the results.
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5.
  • Knudsen, H. H., et al. (författare)
  • Beta-decay of 13O
  • 2005
  • Ingår i: Physical Review C. Nuclear Physics. - 0556-2813. ; 72:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The beta decay of O-13 has been studied at the IGISOL facility of the Jyvaskyla accelerator centre (Finland). By developing a low-energy isotope-separated beam of O-13 and using a modern segmented charged-particle detector array an improved measurement of the delayed proton spectrum was possible. Protons with energy up to more than 12 MeV are measured and the corresponding log(ft) values extracted. A revised decay scheme is constructed. The connection to molecular states and the shell model is discussed.
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6.
  • Madurga, M., et al. (författare)
  • Study of $[$beta$]$-delayed 3-body and 5-body breakup channels observed in the decay of 11Li
  • 2008
  • Ingår i: Nuclear Physics A. ; 810:1-4, s. 1-12
  • Tidskriftsartikel (refereegranskat)abstract
    • The @b-delayed charged particle emission from 11Li has been studied with emphasis on the three-body n@a6He and five-body 2@a3n channels from the 10.59 and 18.15 MeV states in 11Be. Monte Carlo simulations using an R-matrix formalism lead to the conclusion that the AHe resonance states play a significant role in the break-up of these states. The results exclude an earlier assumption of a phase-space description of the break-up process of the 18.15 MeV state. Evidence for extra sequential decay paths is found for both states.
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7.
  • Madurga, M., et al. (författare)
  • Study of β-delayed charged particle emission of 11Li: Evidence of new decay channels
  • 2008
  • Ingår i: Journal of Physics: Conference Series. - 17426588. ; 111:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The break-up of the 18.2 MeV state in 11Be was studied in a 11Li β-decay experiment. We report here on the study of the dominating breakup channels involving na6He or 3n2α in the final state, with special emphasis dedicated in this contribution to the three-particle channel. The two emitted charged particles were detected in coincidence using a highly segmented experimental set-up. The observed experimental energy-vs-energy scatter plot indicates a sequential breakup where nuclei of mass 4, alpha particles, and mass 7, 7He, are involved. A Monte-Carlo simulation of the sequential channel, 11Be* → α + 7He → nα6He was performed and compared to the experimental data and to a simulation of the direct break-up of the 18.2 MeV state nα6He by phase space energy distribution. The energy-versus-energy plot are explained by the sequential simulation but not by the phase space simulation. © 2008 IOP Publishing Ltd.
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8.
  • Prezado, Y., et al. (författare)
  • Low-lying resonance states in the Be-9 continuum
  • 2005
  • Ingår i: Physics Letters B. - 0370-2693. ; 618:1-4, s. 43-50
  • Tidskriftsartikel (refereegranskat)abstract
    • Excited states in Be-9 from 2 to 9 MeV are studied via beta delayed particle emission from Li-9. The broad overlapping particle unbound states are investigated using an extension of an experimental method developed for dealing with three-body decays of broad isolated levels. The results confirm the existence of a broad state at 5 MeV, with a width of 2 MeV. Angular correlations are used for firm spin determinations for this and other levels. (c) 2005 Elsevier B.V. All rights reserved.
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