Low-energy dipole strength in even-even 152-164Dy isotopes within the quasiparticle random phase approximation (QRPA) including symmetry restoring interactions

A systematic study of the low-lying magnetic (M1) and electric dipole (E1) transitions from ground- to excited-states in the doubly-even 152-164Dy isotopes has been performed within the framework of the rotational (RI-), translational and Galilean invariant (TGI-) Quasiparticle Random Phase Approximation (QRPA). According to the results of the calculations dipole strength is fragmented over several states in 2-4 MeV interval and as a rule, one-phonon Iπ=1+ states are rather fragmented than the one-phonon states with Iπ=1−. It is found that even though almost all the M1 strengths are dominated by the orbital motion, the weaker contributions from spin motion plays a relatively major role in shaping the M1 spectra due to its constructive interference with orbital motion in these energies. For 160,162,164Dy the calculated total M1 transition strengths, centroid energies of M1 resonance and gamma widths at the energies between 2 and 4 MeV are in fair agreement with relevant experiment data. It has been shown that in addition to the ΔK=0E1 transitions there are also E1 transitions with ΔK=1 in the low-energy E1 spectrum of all the even-even Dy isotopes under investigation.