NUCLEAR SHAPE PROPERTIES OF THE EVEN–EVEN NEUTRON-RICH RARE-EARTH NUCLEI

Abstract

The physical properties of the nuclear shape have been investigated through the charge square radius (<r2>) and the quadrupole (Q2) and hexadecapole (Q4) moments of the even–even neutron-rich rare-earth nuclei. The single-particle energies used are those of a deformed Woods–Saxon mean-field. The pairing effects have been included by means of an exact projection method. The model has been tested for the "ordinary" nuclei near the shell closure N = 82 and has correctly reproduced the experimental data and particularly the "Kink" effect. The study has then been extended to the neutron-rich nuclei and has shown a stability of the <r2> and Q2 results for N≃100 which may be attributed to the existence of a new magic number. On the other hand, a saturation of the prolate shape appears around N = 108 for the elements Nd , Sm and Gd and near N = 102 for the Dy , Er and Yb . These observations could not be confirmed by the investigation of the hexadecapole moment.