[en] M1 excitations in the ⁹⁰Zr nucleus have been studied in a photon-scattering experiment with monoenergetic and 100% linearly-polarized beams from 7 to 11 MeV. More than 40 J^π = 1+ states were identified for the first time from the observed ground-state transitions revealing the fine structure of the giant M1 resonance with center of gravity of 9 MeV and sum strength of 3.8(3) μ²_N. The results of the present work are compared with predictions from the shell model and the quasi-particle random-phase approximation.

[en] High resolution and sensitivity studies of the nuclear dipole response in ¹³⁸Ba have been performed in (γ, γ') experiment. The electric dipole character of the 'pygmy' mode was experimentally verified for excitations from 4.0 to 8.5 MeV. Experimental findings have been compared with the quasiparticle phonon model. A new understanding about the character and the evolution of the pygmy resonance emerges from comparison of the experimental results with the theoretical calculations.

[en] Dipole-strength distributions in the stable even-mass molybdenum isotopes up to the neutron-separation energies have been studied in photon-scattering experiments with bremsstrahlung at the superconducting electron accelerator ELBE at the Research Center Dresden-Rossendorf, Germany, and with mono-energetic photon beams at the High Intensity Gamma-ray Source facility at Triangle Universities Nuclear Laboratory. In order to determine the dipole-strength distribution, statistical methods were developed for the analysis of the measured spectra. The data obtained for the stable even-mass molybdenum isotopes from the present (γ,γ') experiments are combined with (γ,n) cross sections from the literature resulting in a photoabsorption cross section covering the full range from about 4 to 15 MeV, which is of interest for nuclear structure as well as for nuclear astrophysics network calculations. Novel information about the low-energy tail of the Giant Dipole Resonance and the energy spreading of its strength is derived.

[en] Properties of low-energy dipole states in ²³²Th have been investigated with the nuclear resonance fluorescence technique. The present work used monoenergetic γ-ray beams at energies of 2-4 MeV from the high-intensity γ-ray source at Triangle Universities Nuclear Laboratory. Over 40 transitions corresponding to deexcitation to the ground state and first excited state were observed for the first time. Excitation energies, integrated cross sections, decay widths, branching ratios, and transition strengths for those states in ²³²Th were determined and compared with quasiparticle random-phase-approximation calculations. A large number of E1 transitions were observed for the first time in actinide nuclei with summed strength of 3.28(69)x10^-3 e² fm². The observed summed M1 strength of 4.26(63)μ_N² is in good agreement with the other actinides and with the systematics of the scissors mode in deformed rare-earth nuclei.

[en] High-sensitivity studies of E1 and M1 transitions observed in the reaction ¹³⁸Ba(γ-vector,γ^') at energies below the one-neutron separation energy have been performed using the nearly monoenergetic and 100% linearly polarized photon beams of the HIγ-vectorS facility. The electric dipole character of the so-called 'pygmy' dipole resonance was experimentally verified for excitations from 4.0 to 8.6 MeV. The fine structure of the M1'spin-flip' mode was observed for the first time in N=82 nuclei.

[en] The photodisintegration cross section of the radioactive nucleus ²⁴¹Am has been obtained using activation techniques and monoenergetic γ-ray beams from the HIγS facility. The induced activity of ²⁴⁰Am produced via the ²⁴¹Am(γ,n) reaction was measured in the energy interval from 9 to 16 MeV utilizing high-resolution γ-ray spectroscopy. The experimental data for the ²⁴¹Am(γ,n) reaction in the giant dipole resonance energy region are compared with statistical nuclear-model calculations.

[en] Gamma-ray transitions in ²³⁵U were measured using the (γ,γ^') reaction below 3 MeV. The nuclear-resonance-fluorescence experiment was carried out at the High-Intensity γ-ray Source facility using nearly monoenergetic and circularly polarized photon beams. More than 20 transitions corresponding to deexcitations to the ground state and low-lying levels in ²³⁵U were observed. The integrated cross sections to the excited levels and intensities of branching transitions were deduced. The experimental results are compared with predictions from a quasiparticle random-phase approximation in a deformed basis.