Dipole And Electric Quadrupole Excitations In Ca-40,Ca-48

Photon scattering experiments have been performed to investigate the structure of the two doubly magic nuclei Ca-40,Ca-48. The method is highly selective to induce low-order multipole transitions, i.e., E1, M1, and E2 from the ground state. We determined the energies and spins of excited states and the absolute strengths of the gamma decays in a model independent way. We find the summed electric dipole strengths below 10 MeV to exhaust the energy weighted sum rule by 0.023 and 0.27%, respectively. The summed electric quadrupole strengths are SigmaB(E2)up arrow = 332 e(2) fm(4) and 407 e(2) fm(4) for Ca-40 and Ca-48, respectively. In order to explain the difference in the E1 strengths of the two isotopes several theoretical models are discussed.