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  • 25.90  (3)
  • 25.00
  • 34.50.Bw
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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
    Isotopic dependence of electron screening in fusion reactions (1992)
    Springer
    The European physical journal 342 (1992), S. 471-482 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 25.00
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The fusion reactions6Li(p, α)3He,6Li(d, α)4He, and7Li(p, α)4He have been studied over the c.m. energy rangeE=10 to 1450 keV. Each reaction involved the use of hydrogen projectiles and LiF solid targets as well as Li projectiles and hydrogen molecular gas targets. In all cases the effects of electron screening on the low-energy fusion cross sections (exponential enhancement) have been observed; the effects are somewhat stronger in the case of atomicp ord projectiles compared to the case of molecularH 2 orD 2 gas targets. If isotopic effects on electron screening are negligible, all three reactions should exhibit the same enhancements for each set of experimental techniques. The measurements confirmed this expectation to a large extent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01294958
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  • 4
    Digitale Medien
    Digitale Medien
    Destruction of26Al in explosive nucleosynthesis (1986)
    Springer
    The European physical journal 323 (1986), S. 1-11 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 25.90 ; 95.90
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The26Al(n, p)26Mg reaction has been studied using neutron spectra which closely resembled Maxwell-Boltzmann (M.-B.) distributions with thermal energies ofkT=40 ×10−6, 31 and 71 keV and also forE n =270–350 keV. These energies correspond to stellar temperaturesT 9=4.6×10−7, 0.36, 0.82 and 3.1–4.1, whereT 9 is in units of 109 K. The partial cross sections for thep 0-(p 1-)transition are found to equal 26±10(1,850 ±150), 13±6(124±17), 16±13(84±14) and 21±8(72±15) mb for the above neutron spectra, respectively. The astrophysical reaction rate is determined for the combinedp 0- andp 1-transitions to beN A 〈σν〉=(0.324±0.026, 20.5±2.7, 22.6±4.3 and 38.7±11.1) ×106 cm3 mole−1 s−1. The results are compared with previous investigations and with statistical model calculations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01294550
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  • 5
    Digitale Medien
    Digitale Medien
    Monte Carlo simulations of the Lewis effect (1990)
    Springer
    The European physical journal 336 (1990), S. 403-410 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 34.50.Bw
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Recent experiments measuring the thick-target yield curve of narrow resonances in (p, γ) reactions on23Na,26Mg and27Al nuclei clearly show the Lewis effect. We have studied this effect theoretically on the basis of a Monte Carlo simulation of the nuclear and electronic energy loss curve in the target. We are able to reproduce the experimental data qualitatively. We discuss possible implications of precision measurements of the Lewis effect.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01294114
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