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  • 25.90  (2)
  • 21.60G  (1)
  • 24.10.Eq  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): 25.90 ; 97.10.Cv
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01289572
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  • 2
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): 24.30 ; 25.90
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01294294
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  • 3
    Digitale Medien
    Digitale Medien
    Resonant and intrastate transitions to the 2+ state in8Be (1986)
    Springer
    The European physical journal 324 (1986), S. 307-310 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 23.20 ; 27.10 ; 21.60G
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We have studied resonant, intrastate and non-resonant bremsstrahlungγ-ray transitions leading to the 2+ state in8Be atE x=2.94 MeV. We find aγ-width of Γ γ =0.45 eV for the 4+ state in8Be, corresponding to anE 2 strength of 19 W.u. For the intrastateγ-ray transition within the 2+ resonance we predict a maximum cross section of 2.5 nb atE≈3.3 MeV. An experimental observation of this novel type ofγ-ray emission, however, appears to be difficult due to the dominance of competing resonant and direct capture processes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01294584
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  • 4
    Digitale Medien
    Digitale Medien
    The3He(d,p) α reaction at astrophysical energies (1989)
    Springer
    The European physical journal 333 (1989), S. 219-227 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 21.60.Gx ; 25.55.-e ; 24.10.Eq
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We have performed a microscopic study of the3He(d,p) α reaction at astrophysical energies within the framework of the Resonating Group Method adopting three different effective nucleon-nucleon interactions. The calculations suggest that the low-energy3He(d,p) α cross section is in good approximation given by the contribution arising from the 3/2+ resonant state atE R =245 keV. In fact, the low-energy data can be better (and more physically) described by a single Breit-Wigner resonance parametrization than by a polynomial fit. Our fit to the3He(d,p) α cross section results in a noticeable reduction in the uncertainties of the resonance parameters of the 3/2+ resonant state as well as in a significantly improved extrapolation of the data to astrophysically important energies. On the basis of this extrapolation we were able to quantitatively deduce the enhancement of the low-energy cross section due to electron screening effects from the data of Krauss et al. and Engstler et al. These experimental enhancement factors were compared with various theoretical models which are all based on the Born-Oppenheimer approximation. As the models underestimate the observed enhancement we suggest that the theoretical study of electron screening effects requires a dynamical treatment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01565154
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