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Träfflista för sökning "WFRF:(Wilhelmsen Rolander Katarina 1962 ) srt2:(1993-1994)"

Sökning: WFRF:(Wilhelmsen Rolander Katarina 1962 ) > (1993-1994)

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1.
  • Anne, R., et al. (författare)
  • Dissociation Reactions of the Be-11 One-Neutron Halo - the Interplay between Structure and Reaction-Mechanism
  • 1993
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 304:1-2, s. 55-59
  • Tidskriftsartikel (refereegranskat)abstract
    • The angular distributions of the forward neutrons in the exclusive (Be-10 + n) channel have been measured. They can be accounted for quantitatively and without free parameters in terms of Coulomb and diffraction dissociation. The results show that the transverse momentum distributions result from an interplay between the tail of the wave function (the halo) and the reaction mechanism.
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2.
  • Anne, R., et al. (författare)
  • Exclusive and Restricted-Inclusive Reactions Involving the Be-11 One-Neutron Halo
  • 1994
  • Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 575:1, s. 125-154
  • Tidskriftsartikel (refereegranskat)abstract
    • Reactions of a 41 MeV/u beam of the radioactive halo nucleus Be-11 have been studied with a counter telescope coupled to an array of neutron detectors covering angles up to 97-degrees. The technique allows to determine single-neutron inclusive and exclusive angular distributions. The targets (Be, Ti and Au) were chosen to illustrate the relative roles played by nuclear and Coulomb mechanisms. The channels leading to Be-10, the dissociation channels, correspond to impact parameters larger than the sum of the radii of the target and the Be-10 core. It is shown that for the dissociation process it is possible to account almost quantitatively for the integral, single- and double-differential cross sections from models without free parameters including the Coulomb, Serber and Glauber (diffraction-dissociation) mechanisms. The neutron distributions from the nondissociative reaction channels show little individuality and it is convenient to group them together as the channel ''neutron plus anything different from Be-10''. We refer to these as ''restricted-inclusive'' reactions. These seem to be a promising tool for obtaining accurate information on the halo wave function in momentum coordinates.
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3.
  • Borge, M. J. G., et al. (författare)
  • Study of Charged-Particles Emitted in the Beta-Decay of He-6,He-8
  • 1993
  • Ingår i: Nuclear Physics A. - 0375-9474. ; 560:2, s. 664-676
  • Tidskriftsartikel (refereegranskat)abstract
    • The beta-delayed charged particle spectra from He-6 and He-8 were measured with a telescope consisting of a gas counter and a Si surface barrier detector. Beta-delayed deuterons and tritons are emitted in the two cases with branching ratios of (7.6 +/- 0.6) x 10(-6), E(d) > 350 keV and (8.0 +/- 0.5) x 10(-3), respectively. Both spectra present anomalies that must be due to the special structure of these nuclei (an alpha core surrounded by several neutrons).
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4.
  • Keller, H., et al. (författare)
  • Search for Forbidden Beta-Decays of the Drip-Line Nucleus Be-12
  • 1994
  • Ingår i: Zeitschrift fur Physik A Hadrons and Nuclei. - 1431-5831 .- 0939-7922. ; 348:1, s. 61-62
  • Tidskriftsartikel (refereegranskat)abstract
    • Beta-coincident gamma-rays have been measured from implanted pure samples of Be-12 separated at the LISE3 spectrometer at GANIL. An intensity of 0.040(26)% can be estimated for the branching ratio of the isospin forbidden pure-Fermi transition to the 0+ excited state of B-12 and of 0.008(6) % of the transition to the 1- excited state. Both are taken to represent upper limits. The halflife has been re-measured to be 26.1(2.4) ms.
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5.
  • Wilhelmsen Rolander, Katarina, 1962 (författare)
  • Neutron Halo Nuclei
  • 1993
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In light nuclei close to the neutron drip-line a spatially extended neutron distribution, the neutron, halo occurs. This is due to the relatively small binding energy of the last neutrons which makes possible quantum mechanical tunnelling of the last neutron(s) far away from the nuclear core. There are two main paths in the experimental study of the structure of these nuclei: reactions with radioactive nuclear beams and beta-decays. In reaction studies the momentum distributions from the fragments of reactions between halo nuclei and targets are studied. Results from measurements of (mainly) neutrons from the break-up of the two-neutron halo nucleus 11Li and 11Be with a single neutron halo are presented here. For 11Li data from reactions at 29 MeV/B on three different targets Be, Ni and Au are shown. All the angular distributions of the neutrons are narrow. In reactions of 41 MeV/B 11Be it is clearly seen that different reaction mechanisms are present for different charge of the target. For low Z targets nuclear dissociation reactions dominate yielding board neutron distributions. For targets with high proton number the main contributions is Coulomb dissociation, giving narrow angular distributions. A systematic trend in the .beta.-decay of drip-line nuclei is very large beta-feeding to highly excited states in the daughter nuclei. When states above the separation energy of one or several nucleons are fed, beta-delayed particle emission will occur. Energy spectra of .beta.-delayed particles are analysed to yield information about nuclear structure. In this work is presented experimental data about beta-delayed charged particles, emitted in the decays of 6,8He and 11Li. In the decay of 6He .beta.-delayed deuteron emission was identified for the first time. For 8He and 11Li new data concerning the triton branching ratios are presented. It is also shown that there could be a branch of. beta.-delayed deuterons present in the decay of 11Li , which might be interpreted as the peripheral beta-decay of the two neutron halo.
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