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  • 25.90  (3)
  • 25.40  (2)
  • 12.40.Qq  (1)
  • 21.60.Gx  (1)
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Keywords
  • 1
    Electronic Resource
    Electronic Resource
    The3He(d,p) α reaction at astrophysical energies (1989)
    Springer
    The European physical journal 333 (1989), S. 219-227 
    Details
    ISSN: 1434-601X
    Keywords: 21.60.Gx ; 25.55.-e ; 24.10.Eq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01565154
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of electron screening and resonances in (p, α) reactions on10B and11B at thermal energies (1993)
    Springer
    The European physical journal 345 (1993), S. 231-242 
    Details
    ISSN: 1434-601X
    Keywords: 25.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The fusion reactions10B(p, α)7Be and11B(p, α)8Be have been studied over the c.m. energy range E=17 to 134 keV using intense proton beams and thick solid targets. In the case of11B(p, α)8Be the low-energy data in terms of the astrophysical S(E) factor show an exponential enhancement (up to a factor of 1.9) due to the effects of electron screening, where the deduced screening potential is larger than expected. In the case of10B(p, α)7Be the low-energy data exhibit an enhancement by more than a factor of 200, which cannot be explained by the effects of electron screening. The enhancement arises here from the high-energy tail of an expecteds-wave resonance at ER=10 keV. The results offer an improved prospect for this reaction as advanced fuel in future fusion reactors than previously envisioned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01293350
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The S(E) factor of7Li(p, γ)8Be and consequences for S(E) extrapolation in7Be(p, γ0)8B (1995)
    Springer
    The European physical journal 351 (1995), S. 229-236 
    Details
    ISSN: 1434-601X
    Keywords: 25.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Excitation functions and forward-backward anisotropies have been measured for the7Li(p, γ)8Be capture reaction over the proton energy rangeE p =100 to 1500 keV, using a 4π summing crystal and Ge(Li) detectors, respectively. The data show at all energies the presence of El and M1 capture amplitudes arising from the direct capture (DC) process and theE R =441 and 1030 keV resonances, respectively. Due to the observed DC process, the present data increase significantly the reaction rates (up to a factor of 110) compared to values given in the compilation. The data and their analyses remove the recent criticism on DC model calculations, which had implied a significant reduction in the extrapolated S(E) factor for7Be(p,γ)B and thus in the predicted flux of high-energy solar neutrinos; thus, the solar neutrino problem is still with us.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01289534
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Search for the 70 keV resonance in17O(p, α)14N (1992)
    Springer
    The European physical journal 343 (1992), S. 483-487 
    Details
    ISSN: 1434-601X
    Keywords: 12.40.Qq ; 13.25.+m ; 14.40.Cs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A direct search for theE R =70 keV resonance in17O(p, α)14N was carried out using17O enriched Ta2O5 targets in combination with a 1 mA proton beam and suitable detectors of large solid angle. The observed upper limit for the resonance strength isωγ≤8×10−10 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01289827
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  • 6
    Electronic Resource
    Electronic Resource
    Destruction of26Al in explosive nucleosynthesis (1986)
    Springer
    The European physical journal 323 (1986), S. 1-11 
    Details
    ISSN: 1434-601X
    Keywords: 25.90 ; 95.90
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294550
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  • 7
    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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