Measurement of the Dipole and Electric Quadrupole Strength Distributions up to 10 MeV in the Doubly Magic Nuclei40Caand48Ca

The doubly magic nuclei ${}^{40}\mathrm{Ca}$ and ${}^{48}\mathrm{Ca}$ have been studied in high resolution photon scattering experiments. We have derived absolute dipole and quadrupole excitation strengths up to 10 MeV. Evidence was found for a two-phonon quadrupole-octupole state in ${}^{48}\mathrm{Ca}$. At higher energies in contrast to ${}^{40}\mathrm{Ca}$, a concentration of dipole strength is observed in ${}^{48}\mathrm{Ca}$ which is discussed in terms of a pygmy resonance originating from the large neutron excess.