Dipole and quadrupole excitations in 88Sr up to 6.8 MeV

Dipole and quadrupole excitations in the semimagic N=50 Nucleus ⁸⁸Sr were investigated at the superconducting Darmsatdt linear accelerator S-DALINAC with bremsstrahlung of an endpoint energy of 6.8 MeV. Many new dipole excitations could be identified, and their reduced transition probabilities were determined. The experimental findings are discussed in the context of quasiparticle-phonon-model and shell-model calculations. A breaking of the N=50 core is essential to describe the structure of the observed excitations. The two-phonon quadrupole-octupole J^pi=1^- state exhibits unusual features which are presently not understood.