T. Eckert

Lifetimes of two-phonon 1− states in even N = 82 nuclei

Abstract Photon scattering experiments on the semi magic nuclei 138 Ba and 140 Ce have been performed at the bremsstrahlung facility of the Stuttgart Dynamitron. Two-phonon 1 − states were excited at 4.026 and 3.643 MeV excitation energy respectively as well as a number of 2 + states between 2 and 4 MeV. Lifetimes and upper limits for the decay to other low-lying states were extracted from the data and are compared to lifetimes given in the literature. The systematics of B (E1) values and energies of the 1 − two-phonon states is analysed using additional data from previously published (γ, γ′) experiments on the neighbouring isotones 142 Nd and 144 Sm.

The scissors mode and other magnetic and electric dipole excitations in the transitional nuclei 178,180Hf

Abstract Photon scattering experiments have been performed on the heavy deformed nuclei 178,180 Hf using an E γ K quantum numbers, dipole excitation strengths, and level widths, have been extracted from the scattering cross sections. From the measured level widths lifetimes of 67 levels can be deduced. The excitation strength of the scissors mode is discussed and extends the systematics from the neighboring rare earth nuclei. Besides the ΔK = 1 excitations other dipole excitations have been observed that are distinguished from the scissors mode states by their different decay behavior.

Systematics of Low-Lying Dipole Strength in Heavy Nuclei from Nuclear Resonance Fluorescence Experiments

Low-lying dipole excitations in heavy nuclei were systematically investigated in nuclear resonance fluorescence (NRF) experiments at the bremsstrahlung facility installed at the Stuttgart 4.3 MeV DYNAMITRON accelerator. The systematics of the Ml Scissors Mode in deformed odd-mass nuclei is presented. New results are reported on strong El excitations in spherical semi-magic Z=50 isotopes.