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  • 25.90  (3)
  • 27.10  (3)
  • 97.10  (2)
  • 97.10.Cv  (2)
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Keywords
  • 1
    Electronic Resource
    Electronic Resource
    High resolution study of24Mg(p, d)23Mg for the Ne-E problem (1994)
    Springer
    The European physical journal 348 (1994), S. 59-60 
    Details
    ISSN: 1434-601X
    Keywords: 27.30.+t ; 97.10.Cv ; 97.10.Tk ; 97.30.Qt ; 98.58.Ca
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Nuclear levels of23Mg near and above the proton threshold were investigated with high resolution. A new level has been identified at 7.643 MeV (66 keV above the proton threshold) with a possible Jπ=(3/2, 5/2)+. Some other spin-parity and excitation-energy assignments are also made. These results enable the reaction rate estimate of22Na(p,γ)23Mg with much smaller uncertainties, which is critical for the Ne-E problem in nuclear astrophysics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01291654
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    Paper (German National Licenses)
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  • 2
    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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    Paper (German National Licenses)
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  • 3
    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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  • 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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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Absolute cross section of the3He(α,γ)7Be reaction (1988)
    Springer
    The European physical journal 329 (1988), S. 243-254 
    Details
    ISSN: 1434-601X
    Keywords: 25.55.-e ; 27.10 ; 27.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The absolute cross section σ(E) of the3He(α, γ)7Be reaction has been measured fromE c.m. =195 to 686 keV. The studies employed both a supersonic jet gas target and an extended gas target, and were carried out by the observation of the prompt capture γ-ray transitions as well as the7Be residual nuclei. The absolute cross sections deduced from the capture γ-rays are in good agreement with most previous work and remove a discrepancy with other earlier work. In comparison, the σ(E) values obtained from the7Be residual nuclei are systematically higher, suggesting a small production of additional7Be by contaminant reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01283781
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Resonant and intrastate transitions to the 2+ state in8Be (1986)
    Springer
    The European physical journal 324 (1986), S. 307-310 
    Details
    ISSN: 1434-601X
    Keywords: 23.20 ; 27.10 ; 21.60G
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294584
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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Influence of theD and6Li quadrupole moments on theD(α,γ)6Li stellar reaction rate (1986)
    Springer
    The European physical journal 325 (1986), S. 193-196 
    Details
    ISSN: 1434-601X
    Keywords: 23.20 ; 27.10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have studied theD(α, γ)6Li reaction at stellar energies within a potential model. Our calculation improves previous investigations as we explicitely take into account the internal quadrupole moment of the deuteron and ad-state component in the6Li ground state. We reproduce the experimental data for energiesE〈3 MeV. We find, however, that our improvements represent only minor corrections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01289650
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    Paper (German National Licenses)
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