Explosive Nucleosynthesis with Unstable Nuclei - Complementary Studies Using Low- and Intermediate-Energy Unstable Nuclear Beams -

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Using beams of unstable nuclei provided by RIKEN Ring Cyclotron with intermediate energies and by Cyclotron complex of Louvain la Neuve with low energies, explosive nuclear burning processes have been studied experimentally. The Coulomb dissociation method was employed at RIKEN for an extensive study of the process ^<208>Pb(^8B,^7Be, p)^<208>Pb, which simulate the ^7Be(p, gamma)^8B reaction, a key process for the solar neutrino problem. Our results suggest very small E2 component, which has been estimated theoretically to cause a serious problem for ^8B Coulomb dissociation results. A new determination of S_<17> will be achieved by the second experiment. We also performed an experiment of ^<12>N dissociation related to the hot pp mode burning process.A direct measurement of the reaction ^<19>Ne(p, gamma)^<20>Na was performed at Louvain la Neuve. This reaction was regarded as a key of mass flow from CNO to NeNa region. The experimental could only give an upper limit of the cross section, which is already much smaller than predictions. Another direct measurement was performed for the ^<13>N(p, gamma)^<14>O reaction, a key to ignite hot CNO cycle from the regular CNO cycle. This experiment was aimed at providing a fair and precise comparison between the Coulomb dissociation and direct capture methods by improving the accuracy of data, because both methods were once applied for the ^<13>N(p, gamma)^<14>O and the results agreed with each other within errors. A gamma-ray detection setup with a high efficiency was build at Rikkyo and brought to Louvain la Neuve to measure 5.17 MeV gamma-rays from the radiative capture reaction induced by radioactive ^<13>N beams with an hydrogen target. Analysis is in progress.