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  • 25.90  (3)
  • 97.10  (2)
  • 1
    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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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Helium burning of22Ne (1989)
    Springer
    The European physical journal 334 (1989), S. 491-510 
    Details
    ISSN: 1434-601X
    Keywords: 25.55 ; 97.10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The22Ne(α, γ)26Mg and22Ne(α, n)25Mg reactions were investigated forE α(lab) from 0.71 to 2.25 MeV. Neon gas enriched to 99% in22Ne was recirculated in a differentially pumped gas target system of the extended type. Theγ-ray transitions were observed with Ge(Li) detectors and the neutrons with3He ionization chambers. A previously known resonance at ER(lab)=2.05 MeV was verified and 15 new resonances were found in the energy range covered, with the lowest at ER(lab)=0.83 MeV. Information on resonance energies, widths, strengths,γ-ray branching ratios, as well asJ π assignments, is reported. The energy range investigated corresponds to the important temperature range ofT 9 from 0.3 to 1.4 (109 K), for which the astrophysical rates were determined for both reactions. The results show that the ratios of the rates for22Ne(α, n)25Mg and22Ne(α, γ)26Mg are significantly smaller than the previously adopted values, e.g., by at least a factor of 60 nearT 9=0.65. Thus, the22Ne(α, n)25Mg reaction will likely play a smaller role as a neutron source fors-process nucleosynthesis, than has frequently been assumed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294757
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  • 3
    Electronic Resource
    Electronic Resource
    New22Ne(α,n)25Mg-resonances at very low energies relevant for the astrophysical s-process (1991)
    Springer
    The European physical journal 338 (1991), S. 367-368 
    Details
    ISSN: 1434-601X
    Keywords: 25.55 ; 97.10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The 22Ne(α,n)25Mgreaction is thought to be one of the main neutron sources for the astrophysical s-process. Thus cross section data for this reaction have been obtained from near the threshold (E α≈570keV) up toE α=2100 keV using the 4 MV DYNAMITRON accelerator at Stuttgart, the windowless gastarget system RHINOCEROS and a 4π neutron detector. Two new resonances have been observed atE α=623 ± 6 and 838 ± 6 kev, which dominate the reaction rate at T9〈0.3.Possible background reactions are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01288203
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  • 4
    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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  • 5
    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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