Electromagnetic Excitations in Nuclei: From Photon Scattering to Photo-dissociation

In explosive nucleosynthesis temperatures are high enough for photo dissociation reaction to occur, e.g. leading to the production of p- process nuclei. In order to understand the details of element production and element disruption we started an experimental program at the new bremsstrahlung facility of the superconducting electron accelerator ELBE of FZ-Rossendorf, Dresden. The bremsstrahlung facility and the detector setup are designed such that the scattering of photons from nuclei and the photo dissociation of nuclei around the particle separation energies can be studied under optimized background conditions. The results of photon scattering experiments from the Z=42 nuclei 92,98,100-Mo and the N=50 nuclei 88-Sr, 89-Y,Land 90 Zr will be shown and compared to calculations based on a random-phase approximation method for deformed nuclei. In activation measurements with bremsstrahlung at end point energy from 10.5 to 16 MeV (gamma, p), (gamma, n) and (gamma,alpha) reactions of 92,100-Mo. have been studied. The results are compared to recent astrophysical network calculations to investigate if the underproduction of Mo, Ru isotopes in the p- process is due to incorrect nuclear reaction rates.