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  • 21.80.+a  (2)
  • 25.90  (2)
  • 21.30  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical evidence for di-molecular rotational behaviour in the hypernuclei ∑ 8 Li and ∑ 8 Be (1991)
    Springer
    The European physical journal 339 (1991), S. 523-530 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01288436
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of electron screening on low-energy fusion cross sections (1987)
    Springer
    The European physical journal 327 (1987), S. 461-468 
    Details
    ISSN: 1434-601X
    Keywords: 25.90 ; 97.10.Cv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The effects of electron screening on the low-energy cross sections of nuclear fusion reactions of astrophysical interest have been studied within the Born-Oppenheimer approximation using a simplified model. These studies indicate that a significant enhancement of the cross sections can occur already at beam energies, which are about a factor 100 higher than the electron binding energies. Cross sections near such energies can now be measured, in some cases, and several examples are discussed. For an understanding of the low-energy data as well as for a reliable extrapolation of the cross sections (for bare nuclei) to lower energies, the effects of electron screening must be well understood.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01289572
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    AstrophysicalS(E) factor of8Li (α,n 0)11B and inhomogeneous Big Bang nucleosynthesis (1990)
    Springer
    The European physical journal 337 (1990), S. 211-220 
    Details
    ISSN: 1434-601X
    Keywords: 24.30 ; 25.90
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The cross section of the11B(n, α)8Li reaction has been measured atE n=7.6 to 12.6 MeV. The neutron beam was produced via theD(d, n)3He reaction and aBF 3 counter (with naturalB isotopic composition) served both as target for the11B nuclides and as detector for the observation of the delayedα-activity of8Li. The data match well with previous results obtained atE n =12.5 to 20.0 MeV. Using the principle of detailed balance the data were converted to the case of the8Li(α, n 0)11B reaction. The associated astrophysicalS(E) factor is dominated by a resonance atE R=0.58 MeV of widthΓ R =200 keV, withS(E R )=8400 MeV b. ThisS (E R ) value for the n0 channel alone is already three times higher than the constantS(E) factor assumed previously and, thus, strengthens the significance of inhomogeneous Big Bang nucleosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294294
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Pycnonuclear triple-alpha-fusion rate in hypernetted chain Approximation (1992)
    Springer
    The European physical journal 342 (1992), S. 133-140 
    Details
    ISSN: 1434-601X
    Keywords: 21.30 ; 67.20 ; 97.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied the helium plasma in the hypernetted-chain-Approximation considering both short-ranged internuclear and long-ranged Coulomb interactions. The optimal two-particle wave function has been determined in HNC/0 approximation. The two-particle distribution functions, which have been calculated in various orders of HNC/n approximations (n=0, 4, 5), are used to determine the pycnonuclear triple-alpha-fusion rate in the density regime 108 g/cm3≤ρ≤1010 g/cm3, in which the fusing of three alpha-particles to form a12C-nucleus plays an important role in the crust evolution of an accreting old neutron star. Our calculation supports the idea that the helium liquid undergoes a phase transition to stable8Be matter at densities slightly lower thanρ≈3×109 g/ cm3 as the plasma induced screening potential then becomes strong enough to bind the8Be ground state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01288460
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Distortion effects in light hypernuclei (1989)
    Springer
    The European physical journal 334 (1989), S. 221-230 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01294223
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    Paper (German National Licenses)
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