Vortex octupole mode in the kinetic model of collective excitations in nuclei

Abstract

The nature of a new isoscalar octupole resonance found within a kinetic model based on the Vlasov equation for finite Fermi systems with moving surfaces is studied. It is shown that this octupole resonance is due to dynamic effects of the nuclear surface, like the low-energy isoscalar dipole resonance (vortex dipole mode) observed in heavy nuclei. It is found that the velocity field associated with the new octupole resonance has a vortex character in the surface region of the nuclear liquid and, moreover, the vortex motion of nucleons is fragmented into three areas near the nuclear surface. At the same time, the velocity field associated with the high-energy octupole resonance found within our kinetic model displays an octupole deformation form and includes a compression within the nuclear fluid, which is consistent with the corresponding quantum calculations in the random phase approximation.

Keywords

• isoscalar octupole resonances
• kinetic model
• strength function
• dynamic surface effects
• velocity field.