Photo-induced nucleosynthesis: Current problems and experimental approaches

Photon-induced reactions play a key role in the nucleosynthesis of rare neutron-deficient p -nuclei. The paper focuses on , , and reactions which define the corresponding p -process path. The relation between stellar reaction rates and laboratory cross-sections is analyzed for photon-induced reactions and their inverse capture reactions to evaluate various experimental approaches. An improved version S _C(E) of the astrophysical S -factor is suggested which is based on the Coulomb wave functions. S _C(E) avoids the apparent energy dependence which is otherwise obtained for capture reactions on heavy nuclei. It is found that a special type of synchrotron radiation available at SPring-8 that mimics stellar blackbody radiation at billions of kelvins is a promising tool for future experiments. By using the blackbody synchrotron radiation, sufficient event rates for and reactions in the p -process path can be expected. These experiments will provide data to improve the nuclear parameters involved in the statistical model and thus reduce the uncertainties of nucleosynthesis calculations.