On the low-energy electromagnetic dipole modes in <SUP>151,153,155</SUP>Sm Nuclei

The recently observed low-energy magnetic dipole (M1) and electric dipole (E1) excitations in deformed Sm-151,Sm-153,Sm-155 are theoretically analysed. Rotational Invariant (RI-) and Translational- Galilean Invariant (TGI-) Quasiparticle Nuclear Model (QPNM) are used in the calculation of M1 and E1 properties, respectively. Both theories consider monopole pairing between nucleons, and the deformed Woods-Saxon potential is used as the mean-field potential. Pyatov's symmetry restoration procedure is applied in these models to eliminate the spurious modes from the intrinsic nuclear excitations. Model calculations show that although E1 transitions dominate the low-energy dipole spectra of Sm-151,Sm-153,Sm-155, many low-lying M1 transitions exist in these nuclei. It is shown that the most significant contribution to E1 and M1 excitation comes from Delta K = +/- 1 transitions. The theory satisfactorily reproduces the gross features of low-lying dipole modes determined from the Oslo Method analysis of the experimental spectra.