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  • 23.20  (3)
  • 25.40  (2)
  • 21.60.Gx  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    The3He(d,p) α reaction at astrophysical energies (1989)
    Springer
    The European physical journal 333 (1989), S. 219-227 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 21.60.Gx ; 25.55.-e ; 24.10.Eq
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01565154
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  • 2
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): 25.40
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01293350
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  • 3
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): 25.40
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01289534
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  • 4
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): 23.20 ; 27.10
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01289650
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Resonant and intrastate transitions to the 2+ state in8Be (1986)
    Springer
    The European physical journal 324 (1986), S. 307-310 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 23.20 ; 27.10 ; 21.60G
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01294584
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  • 6
    Digitale Medien
    Digitale Medien
    Intrastate γ-transitions: A spectroscopic tool? (1987)
    Springer
    The European physical journal 328 (1987), S. 291-299 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 23.20 ; 21.10.-k
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In the framework of a potential model we have calculated the various bremsstrahlung cross sections into the5Li ground state, includingM 1 andE 2 γ-transitions leading from the high energy wing of the5Li ground state resonance into states belonging to the same resonance at lower energy (intrastate transition). Our calculation supports the hypothesis of Schmalbrock et al. [1] that intrastate transitions ofM 1 andE 2 multipolarity exist. While we find a maximum cross section of roughly 1.4 nb for theE 2 transition, we predict the cross sections forM 1 intrastate transition to be less than 3·10−5nb. An experimental observation of the intrastate γ-ray emission appears to be very difficult due to the dominance of competing resonant (M 1) and direct (E 1) capture processes. Schmalbrock et al. have suggested to deduce magnetic dipole and electric quadrupole moments of resonant states from the measurements of the respectiveM 1 andE 2 intrastate transitions. We will show that theM 1 intrastate cross sections do not yield the appropriate information to determine the magnetic dipole moment. We will also discuss thatE 2 intrastate transitions do not seem to be a suited tool to find the quadrupole moment of an unstable state.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01290497
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