No abstract available

[en] The ¹⁴N(p,γ)¹⁵O low-energy S-factor is analyzed using the R-matrix model. We find that the g.s. contribution is less than previously reported. The S-factor is mainly given by the 6.79 MeV state contribution which is determined by its asymptotic normalization constant (ANC). Consequently, the S-factor at zero energy is lower by a factor of 1.7 compared to the values given in recent compilations. This result may affect the nucleosynthesis and time scale evolution in massive stars. New measurements of the ¹⁴N(p,γ)¹⁵O cross section over a wide energy range, and especially at low energies, are highly desirable. Significant improvement could be also obtained from the ANC measurement of the 6.79 MeV state

[en] We briefly report on the program and present results of the European network for the evaluation and compilation of astrophysical nuclear reaction rates. (orig.)

[en] The energy loss of ⁹Be, ¹¹B, ¹²C, ¹⁴N, ¹⁶O, ¹⁹F and ²⁰Ne ions at 1 MeV per nucleon in C, Al, Ni, CH₂ (polyethylene) and PVC (polyvynilchloride) have been measured at the Louvain-la-Neuve cyclotron facility. Stopping powers are given relative to the one for 5.486 MeV ⁴He ions with an uncertainty of at most 1%. Absolute stopping powers are also provided. We compare our results with previous experimental data and with semi-empirical models

[en] A simple formulation of low-energy transfer reactions is developed within the R-matrix method. This parametrization is shown to provide the energy dependence of the S-factor with a good accuracy. We study the ³He(³He,2p)⁴He, ²H(d,p)³H and ⁶Li(p,α)³He reactions as typical examples. From these fits we analyze electron screening effects. Screening potentials are determined with an error analysis based on experimental errors as well as on theoretical uncertainties. (orig.)

No abstract available

[en] Thin Al foils of 50 μg/cm² thickness were implanted with ⁴He ions with fluences ranging between 10¹⁷ and 10¹⁸ atoms/cm². The bulk He contents was measured by the Rutherford backscattering method. The He implantation profile versus depth was obtained by elastic recoil detection analysis. He-implanted targets will be used to measure (α,γ) reactions of astrophysical interest, in inverse kinematics

[en] Studies of the dissociation of fast projectiles in the Coulomb field of a heavy target nucleus have been proposed as an alternative access to radiative capture cross sections of astrophysical relevance. Instead of measuring the cross section A+b → C+γ, one considers the photodissociation process C+γ → A+b. Compared with the direct process, the cross section of the inverse one is enhanced due to the high density of virtual photons. The Coulomb break-up technique has been applied to radioactive beams in order to determine rates of reactions involved in the hot CNO cycle and the hot pp chain. ¹²N and ¹⁴O radioactive beams were produced through fragmentation of a primary 95.5 MeV/u heavy ion beam, and used to study the rates of the reactions ¹³N+p → ¹⁴O+γ and ¹¹C+p → ¹²N+γ. Nuclear astrophysics requires many cross sections, and one could hope that the Coulomb break-up method would be of a large use. A survey of the most important reaction rates actually required in astrophysics will be made regarding the applicability of the break-up method to extract valuable experimental information

[en] Published in summary form only

[en] The fusion reactions ¹⁰B(p, α) ⁷Be and ¹¹B(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 of ¹¹B(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 of ¹⁰B(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 expected s-wave resonance at E_R=10 keV. The results offer an improved prospect for this reaction as advanced fuel in future fusion reactors than previously envisioned. (orig.)