O. Beck

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.

Strong fragmentation of low-energy electromagnetic excitation strength in Sn-117

Results of nuclear resonance fluorescence experiments on Sn-117 are reported. More than 50 gamma transitions with E gamma < 4 MeV were detected. For the first time microscopic calculations making use of a complete configuration space for low-lying states are performed for a heavy odd-mass spherical nucleus. The theoretical predictions are in good agreement with the data. It is concluded that although the El transitions are the strongest ones also M1 and E2 decays contribute substantially to the observed spectra. In contrast to the neighboring even Sn116-124 nuclei, in Sn-117 the 1(-) component of the two-phonon [2(1)(+) x 3(1)(-)] multiplet built on top of the 1/2(+) ground state is proved to be fragmented.

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.