Dipole strength in 89Y up to the neutron-separation energy

Photoexcitation of the N=50 nucleus 89Y has been performed at the bremsstrahlung facility at the superconducting electron accelerator ELBE at electron energies of Eekin=9.5 and 13.2 MeV. About 250 levels up to the neutron-separation energy were identified. Statistical methods were applied to estimate intensities of inelastic transitions and to correct the intensities of the ground-state transitions for their branching ratios. The photoabsorption cross section derived in this way up to the neutron-separation energy is combined with the photoabsorption cross section obtained from (γ, n) data and provides information about the extension of the giant dipole resonance toward energies below the neutron-separation energy. An enhancement of E1 strength has been found in the range from about 6 to 11 MeV. The experimental photoabsorption cross sections of 89Y and of the neighboring N=50 isotones 88Sr and 90Zr are compared with predictions of the quasiparticle-random-phase approximation