Systematic studies of low lying dipole excitations in 164,166,168,170Er by means of nuclear resonance fluorescence experiments

The photon scattering experiments were performed for the lower energy range up to 4 MeV at the Stuttgart Dynamitron and for the upper energy range up to 12 MeV at the Gent Linear Accelerator. By the measurement on the Er isotopes the systematic studies of the M1 scissor mode were supplemented in the region of the well deformed rare earth nuclei. The fragmentation of the transition strength increases to the lighter Er isotopes. In the measurement on 164Er only states with smaller transition strength than in the other isotopes were observed. Furthermore the summed strength is distinctly smaller than in 166Er