Investigation of low-lying electric dipole strength in the semimagic nucleus ^{44}Ca

The dipole-strength distribution in the semimagic nucleus Ca-44 has been measured up to 10 MeV excitation energy in photon-scattering experiments using bremsstrahlung and monoenergetic 100% linearly polarized photon beams. The combination of both measurements allows a clear determination of spin and parity quantum numbers of the excited states as well as absolute cross sections and transition probabilities. The results show that the majority of the dipole strength in Ca-44 below 10 MeV is due to E1 transitions while M1 strength plays only a minor role. The experimental results are compared to the strength in the neighboring doubly magic nuclei Ca-40,Ca-48 and to microscopic calculations within the extended theory of finite Fermi systems in order to investigate the evolution of the low-lying E1 strength in this isotopic chain. Both, experiment and calculations, show a nontrivial dependence of the total E1 strength as a function of the neutron number.