Deformation effects in toroidal and compression dipole excitations of ${}^{170}$Yb: Skyrme-RPA analysis

Abstract

The effect of nuclear deformation on the isoscalar toroidal and compression dipole modes in prolate ${}^{170}$Yb is studied in the framework of the random-phase-approximation method with a representative set of Skyrme forces (SV-bas, SLy6, SkM${}^{\ast }$ and SkI3). It is shown that the deformation crucially redistributes the strength of both modes. The compression mode has the same sequence of $\hat{I}¼$=0 and 1 branches as the isovector giant dipole resonance where for prolate nuclei the $\hat{I}¼=0$ mode is lower in energy ($\hat{I}¼$ being the projection of the axial momentum of the mode). Instead, the toroidal mode exhibits an anomalous (opposite) sequence where the $\hat{I}¼$=1 branch precedes the $\hat{I}¼$=0 one.

5 pages, 6 figures, submitted to Phys. Scripta