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

Abstract A systematic study of the low-lying magnetic ( M 1) and electric dipole ( E 1) transitions from ground- to excited-states in the doubly-even 152–164 Dy 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 I π = 1 + states are rather fragmented than the one-phonon states with I π = 1 − . It is found that even though almost all the M 1 strengths are dominated by the orbital motion, the weaker contributions from spin motion plays a relatively major role in shaping the M 1 spectra due to its constructive interference with orbital motion in these energies. For 160,162,164 Dy the calculated total M 1 transition strengths, centroid energies of M 1 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 Δ K = 0 E 1 transitions there are also E 1 transitions with Δ K = 1 in the low-energy E 1 spectrum of all the even–even Dy isotopes under investigation.