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 178,180Hf using an Eγ < 4 MeV bremsstrahlung beam as a continuous energy photon source. Numerous dipole excitations have been identified from the spectra of high-resolution Ge γ detectors. Spins, 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.