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  • 1985-1989  (3)
  • 1989  (3)
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  • 1985-1989  (3)
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  • 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
    Screening corrections in cold deuterium fusion rates (1989)
    Springer
    The European physical journal 333 (1989), S. 317-318 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have recalculated the fusion rates of the free deuterium molecule, ion and mesomolecule taking into account the shielding of the Coulomb barrier by the electrons and muon. Electron screening increases the rates by several orders of magnitude. The fusion of hydrogen nuclei is known to be the source of energy of stars occuring in their high-temperature, high-pressure interiors. In terrestrial conditions, one attempts currently to tap this source of nuclear fusion energy by alternative techniques, i.e. high-temperature plasmas or muon-catalyzed fusion. Very recently cold fusion in solids has achieved worldwide attention, since experimental evidence for increased hydrogenic fusion rates in palladium and titanium has been reported[1,2]. These reports have motivated us to reconsider the fusion probability of free hydrogen molecules, ions and mesomolecules, following closely the studies of Refs. [3,4,5]. Our aim however is to improve the previous estimates of the respective fusion rates by taking account of the screening effects of the electrons and muons on the nuclear Coulomb barrier which will turn out to be quite important. As in Ref. [5] we will restrict our numerical results to deuterium only.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294522
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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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    Paper (German National Licenses)
    Fulltext
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