Probing Nuclear Structure and Nuclear Astrophysics with Real Photons

Examples for recent studies of magnetic dipole and electric quadrupole excitations with the nuclear resonance fluorescence technique at the superconducting Darmstadt electron linear accelerator S–DALINAC are given. The properties of the gross and fine structure of the orbital magnetic scissors mode in even and odd-mass nuclei are summarized. Within a test experiment, the decay width of the excited state at 3.908 MeV in F has been studied which might be important for breakout mechanisms from the CNO cycle in heavy main-sequence stars. Medium-mass doubly-magic nuclei exhibit an unusual distribution of electric quadrupole strength below the particle threshold. This is not observed for semi-magic nuclei.