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

Abstract

A systematic study of the low-lying magnetic (M1) and electric dipole (E1) transitions from ground- to 152-164 excited-states in the doubly-even Dy152-164 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-pi = 1(+) states are rather fragmented than the one-phonon states with I-pi = 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 Dy-160(,)162(,)164 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 Delta K = 0 E1 transitions there are also E1 transitions with Delta K = 1 in the low-energy E1 spectrum of all the even-even Dy isotopes under investigation. (C) 2018 Elsevier B.V. All rights reserved.