Vera Derya, Deniz Savran, Janis Endres, Muhsin N. Harakeh, Heiko Hergert, John Kelley, Panagiota Papakonstantinou, Norbert Pietralla, Vladimir Yu. Ponomarev, Robert Roth, Gencho Y. Rusev, Anton P. Tonchev, Werner Tornow, Heinrich Wörtche, Andreas Zilges
- Two different experimental approaches were combined to study the electric dipole strength in the doubly-magic nucleus 48Ca below the neutron threshold. Real-photon scattering experiments using bremsstrahlung up to 9.9 MeV and nearly mono-energetic linearly polarized photons with energies between 6.6 and 9.51 MeV provided strength distribution and parities, and an (α,α' γ) experiment at Eα = 136 MeV gave cross sections for an isoscalar probe. The unexpected difference observed in the dipole response is compared to calculations using the first-order random-phase approximation and points to an energy-dependent isospin character. A strong isoscalar state at 7.6 MeV was identified for the first time supporting a recent theoretical prediction.
