A new approach of a global alpha-optical model potential at energies relevant for astrophysics

The modelling of various astrophysical processes involves large scale network calculations, whose input data are the reaction rates at appropriate temperatures. Due to the lack of experimental reaction cross section data at energies in the Gamow windows for most of the nuclei, either stable or unstable, it is necessary to predict the reaction cross sections and thermonuclear rates by theoretical models. Theoretical estimates of α-induced reaction rates within the framework of the statistical model of Hauser-Feshbach remain highly uncertain essentially due to our poor knowledge of the α-nucleus interaction. As required in many nuclear astrophysics applications, such as the α- or p- process nucleosynthesis, a new global α-optical potential is proposed in order to take into account the strong energy dependence and nuclear structure effects affecting the potential. The new parametrization used to describe the imaginary part of the interaction is shown to improve the predictions of the α-particle transmission factors of relevance in the Hauser-Feshbach model and to reproduce well experimental reaction data at energies of relevance in astrophysical conditions. (authors)