Evidence for enhanced electric dipole excitations in deformed rare earth nuclei near 2.5 MeV

Measurements of the linear polarization of resonantly scattered photons have been used for model independent parity assignments in nuclear resonance fluorescence experiments. The novel result of the present study was the first observation of enhanced electric dipole excitations in the deformed nuclei ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}$ and ${}_{}{}^{162}{}_{}{}^{}\mathrm{Dy}$ at excitation energies of 2.414 and 2.520 MeV, respectively. The transition energies and the enhanced B(E1)↑ strengths of 3 and 5×${10}^{\mathrm{-}3}$ ${\mathit{e}}^2$ ${\mathrm{fm}}^2$ support the interpretation in terms of the predicted new type of collective electric dipole excitations in deformed nuclei due to reflection asymmetric shapes like octupole deformations and/or cluster configurations.