Nuclear astrophysics with radioactive beams at TAMU
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abstract
A major contribution in nuclear astrophysics is expected now and in the near future from the use of radioactive beams. This paper presents an indirect method utilizing radioactive beams to determine the astrophysical 5-factor at the very low energies relevant in stellar processes (tens and hundreds of keV) from measurements at energies more common to the nuclear physics laboratories (10 MeV/nucleon). The Asymptotic Normalization Coefficient (ANC) method consists of the determination from peripheral transfer reactions of the single particle wave function of the outermost charged particle (proton or alpha particle) around a core in its asymptotic region only, as this is the part contributing to nuclear reactions at very low energies. It can be applied to the study of radiative proton or alpha capture reactions, a very important class of stellar reactions. The method is briefly presented along with our recent results in the determination of the astrophysical factor for the proton capture reactions 7Be(p,7)8B and nC(p,7)12N. The first reaction is crucial for the understanding of the solar neutrino production, the second is a reaction that would bypass the mass .4 = 8 gap in the hot pp chains. Our study was done at the K500 superconducting cyclotron of Texas A&M University (TAMU). Proton transfer reactions with radioactive beams 7Be and nC produced with MARS were measured, as well as proton transfer reactions involving stable partners. We present the experiments, then discuss the results and the uncertainties arising from the use of calculated optical potentials between loosely bound radioactive nuclei.
