The 3He(7Be; alpha)6Be reaction and resonances in the unbound nuclei 6Be

Full text: At the present time, one of the most important subjects of nuclear physics at low energies is the investigation of reaction mechanisms with exotic nuclei, nuclei far from beta stability line. The existence of exotic nuclei in stellar environments and interstellar medium opened a broad field of research with consequences in the study of cosmology, stellar evolution, nucleosynthesis in the universe and others fields. This work consists in the study of the transfer and capture reactions, of the nucleons by weakly bound nuclei. These reactions generally occur on the surface of the nucleus, far from the strong interaction, and are therefore called peripheral reactions. This process of radiative capture and some transfer reactions are examples of peripheral reaction. Here the goal is to study the mechanism of these processes in terms of the peripherality of the reaction. We are starting with the study of the resonance effects in neutron and proton capture reactions. In order to calculate the radiative capture cross section we need the wave function of the bound state A + x, where A is some light nuclei and x the proton or neutron. The bound state potential used to generate this wave function is generally represented by a Woods-Saxon potential. However, since we are looking for analytic solution we started the investigation with a square well potential approximation. Since we are dealing with low energy capture reaction, where the wave length λ is much bigger than the diffuseness a of the Woods-Saxon potential. We show that the position of the bound states and resonances in a Woods-Saxon is related to the stationary states of an infinity square well.We study also the dependence of widths of the resonances with the Woods-Saxon parameters. We apply our method to a few real cases of capture reactions. (author)