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  • 21.80.+a  (2)
  • 21.60.Cs  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 334 (1989), S. 1-9 
    ISSN: 1434-601X
    Keywords: 21.60.Cs ; 21.60.Gx ; 23.20.-G
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract StrongB(E1) transitions have been recently observed between states in the18O nucleus which follow roughly the energy sequence of a dimolecular α+14C rotator. These findings have been interpreted by Gai et al. as evidence for a molecular dipole degree of freedom being present in the18O nucleus. However, this idea was contradicted by the results of a microscopic multichannel calculation performed by Descouvemont and Baye which was based on elastic α+14C and inelastic α+14C(2+) many-body cluster wave functions. We have improved this study by performing a microscopic multichannel calculation including additionally an+17O many-body fragmentation in order to enlarge our model space by those shell model components which dominate the structure of the (positive parity)18O ground state band. Like Descouvemont and Baye we find a positive parity α+14C molecular band in18O and, additionally, a rather strong collectivity in the lowest 1−, 3− and 5− states in18O. However, since the internal structure is different within these states, the calculated states should not be interpreted as a negative parity α+14C molecular band. In this perspective, the microscopic multichannel calculations do not support the hypothesis of a molecular dipole degree of freedom being present in the18O nucleus.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 334 (1989), S. 221-230 
    ISSN: 1434-601X
    Keywords: 21.80.+a ; 21.40.+d ; 21.60.Gx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied the particle-bound levels in the hypernucleiΛ 3,4H,Λ 5He,Λ 8Li andΛ 8,9Be in the framework of the full microscopic Resonating Group Method (RGM). In a first step we have solved the respective nuclear many-body problem within the RGM. For each hypernucleus we have then performed a static calculation, in which the nuclear degrees of freedom were kept fixed, and a dynamical calculation in which nuclear degrees of freedom were allowed to vary. The differences between these two studies allowed us to investigate nuclear distortion effects caused by the presence of theΛ-particle. We find the nuclear distortion effects to be inverse proportional to the binding of the nuclear constituents. Thus, the strongest effects are observed forΛ 3H and forΛ 9Be. Our dynamical approach does not show the strong overbinding ofΛ 3H andΛ 9Be as reported in other cluster model studies. Our results for thep-shell hypernuclei agree reasonably well with those obtained in a semi-microscopic Orthogonal Condition Model (OCM) study which used the same effectiveΛN-interaction as employed in our calculation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 339 (1991), S. 523-530 
    ISSN: 1434-601X
    Keywords: 21.80.+a ; 21.60.Gx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have performed microscopic cluster studies of light∑-hypernuclei based on effective nucleon-nucleon and two different sigma-nucleon interactions. Our calculation confirms a bound 0+ state in ∑ 4 He and ∑ 4 H, but reveals no evidence for levels in other partial waves. We have investigated the ∑ 8 Li and ∑ 8 Be hypernuclei in a microscopic 3-cluster approach. For both hypernuclei, our calculation shows that the lowest levels in the partial wavesJ=0–4 are bound or quasibound states of collective nature and show a strong α ∑ 4 H and α + ∑ 4 He clustering. These levels form a sequence of states which can be well interpreted as arising from a rotatingα+ ∑ 4 H orα+ ∑ 4 He di-molecule. Our results are compared to those of similar studies for lightΛ-hypernuclei which do not show evidence for this kind of collective degrees of freedom.
    Type of Medium: Electronic Resource
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