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  • 11
    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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  • 12
    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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  • 13
    Electronic Resource
    Electronic Resource
    Electron screening in thed+3He fusion reaction (1994)
    Springer
    The European physical journal 350 (1994), S. 171-176 
    Details
    ISSN: 1434-601X
    Keywords: 25.55.−e
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Cross section measurements of thed(3He,p)4He reaction have been extended to an energy as low asE cm =5.4 keV. The data have an improved accuracy compared with previous work and confirm the existence of electron screening. The combined analysis of the present and previous data leads to an electron screening potential ofU e =123 ± 9 eV. A similar analysis of previous data for3He(d, p)4He leads toU e =186 ± 9 eV. Both screening potentials differ due to the molecular and atomic aggregate state of the targets involved in these investigations and are significantly larger than expected from available atomic physics models, supporting the general trend in studies of electron screening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01290685
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  • 14
    Electronic Resource
    Electronic Resource
    The3He(α,γ)7Be reaction and the solar neutrino problem (1982)
    Springer
    The European physical journal 304 (1982), S. 307-332 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The capture reaction3He(α,γ)7Be has been investigated in the energy range ofE c.m. =107 to 1,266 keV. The4He or3He beams of up to 300 μA particle current were incident on3He or4He gas targets, respectively. The gas target systems were all of the windowless and recirculating type. Excitation functions have been obtained with the use of an extended-static gas target, while the measurements ofγ-ray angular distributions involved a quasi-point supersonic jet system. The determination of absolute cross sections has been carried out with both types of gas target systems. Theγ-ray yields in the3He(α,γ)7Be reaction were detected using 80 cm3 Ge(Li) detectors. The data lead to a zero-energy intercept of the astrophysicalS(E) factor ofS(0)=0.30±0.03 keV-b. This result reduces the calculated solar neutrino rate by a factor of 1.76.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01421513
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  • 15
    Electronic Resource
    Electronic Resource
    Resonance strengths of some light nuclei (1982)
    Springer
    The European physical journal 305 (1982), S. 319-323 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The strengths of theE c.m.=324 and 829 keV resonances in19F(ρ, αγ)16O have been determined relative to the Rutherford elastic scattering cross section. With these values as standards, the strengths of theE c.m.=259, {pp143} (also 1,106) and 1,259 keV resonances in14N(ρ, γ)15 O,18O(ρp, γy)19F and14N(α, γ)18F were measured, respectively. In addition, the cross section of the direct capture process in16O(ρ, γ)17F atE c.m.=853 keV has been obtained. All measurements were carried out by interchanging the role of projectiles and target nuclei, i.e.14N,16O,18O and19F ion beams of appropriate energies were guided into windowless gas target systems filled with hydrogen or helium gas. The results are compared with previous work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01419080
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  • 16
    Electronic Resource
    Electronic Resource
    Search forγ-ray transitions within the5Li groundstate (1983)
    Springer
    The European physical journal 310 (1983), S. 243-245 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A search forγ-ray transitions within the broad groundstate of5Li has been carried out via the4He(p, γp *)4He reaction atE p (lab)=1.5−7.0 MeV. Differentially pumped gas targets of the extended and quasi-point types have been used. The results show that the set-up and detection techniques utilized are not sensitive enough to observe such intrastate transitions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01415229
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  • 17
    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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  • 18
    Electronic Resource
    Electronic Resource
    The12C+12C reaction at subcoulomb energies (II) (1981)
    Springer
    The European physical journal 303 (1981), S. 305-312 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The reaction12C+12C has been studied in the energy range Ec.m.=2.8–6.3 MeV by charged-particle spectroscopy. Angular distributions of the proton and α-particle exit channels were obtained. The excitation functions do not reveal evidence for the phenomenon of absorption under the barrier. The data have been extrapolated to the energy region of astrophysical interest. The existence of reported and new intermediate resonance structures is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01421528
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  • 19
    Electronic Resource
    Electronic Resource
    Comparison of the fusion reactions12C+20Ne and16O+16O near the Coulomb barrier (1980)
    Springer
    The European physical journal 297 (1980), S. 161-183 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The partial cross sections of heavy residual nuclei produced in the heavy ion fusion of12C+20Ne have been measured atE c.m.=6–15 MeV viaγ-ray spectroscopy with a Ge(Li) detector. Windowless and recirculating gas target systems have been used. The dominant residual nuclei are24Mg,27Al,28Si,30Si,30P and31P, which arise from two- and three-body breakups in the exit channels. The observed excitation functions are smooth in their energy dependence and give no indications for the existence of pronounced resonance structures, in contrast to theoretical predictions. The Coulomb excitation of20Ne served as an intrinsic calibration standard in the determination of absolute partial and total fusion cross sections. The same experimental set-up was also used in the reaction studies of16O+16O atE c.m.=7–14 MeV, going through the same compound nucleus32S at similar excitation energies. The observed energy dependence in the excitation functions is in good agreement with previous work. The total fusion cross section agrees fairly well with two sets of values reported previously, but deviates significantly from other reported absolute cross section values. The relative evaporation distributions of the residual nuclei are similar for both heavy ion reactions. However, the ratio of their total fusion cross sections deviates from model predictions and suggests that compound nucleus formation does depend on the microscopic structure of the colliding nuclei in the entrance channel. From the observed energy dependence of the above ratio, particularly at subcoulomb energies, geometrical effects in the entrance channel (due to deformed and spherical nuclei) appear to be weak. The astrophysical aspects of the data in the context of late stellar nucleosynthesis are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01421473
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  • 20
    Electronic Resource
    Electronic Resource
    Low-energy cross sections for11B(p, 3α) (1987)
    Springer
    The European physical journal 327 (1987), S. 341-355 
    Details
    ISSN: 1434-601X
    Keywords: 25.85.−w ; 24.90.+d ; 95.30.−k
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The11B(p, 3α) reaction has been investigated in the energy range fromE c.m.=22 to 1100 keV with the use of either a proton beam and a11B solid target or with the use of a11B heavy ion beam incident on a hydrogen jet gas target. The reaction mechanisms have been studied via kinematically complete coincidence measurements showing that the reaction proceeds predominantly by a sequential decay via8Be. The measurement of absolute cross sections,α-angular distributions and excitation functions is reported. The astrophysicalS(E) factor has been described by means of an empirical fit to the data, leading to a zero-energy intercept ofS(0)=197±12 MeVb. Conclusions drawn on the use of this reaction as an advanced fuel in fusion reactors remain essentially unchanged by the present data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01284459
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