Dynamic effects of nuclear surface in isoscalar dipole modes

TL;DR

This paper investigates how dynamic surface effects influence isoscalar dipole modes in heavy nuclei using a semiclassical Vlasov model, revealing significant impacts on resonance structures and characterizing different resonance types.

Contribution

It introduces a dynamic-surface approximation within a semiclassical model to analyze surface effects on isoscalar dipole modes in heavy nuclei.

Findings

Dynamic surface effects significantly influence isoscalar dipole modes.

The strength function exhibits a two-resonance structure with energies close to exact calculations.

Velocity field analysis shows vortex and compression characters for low- and high-energy resonances.

Abstract

Dynamic surface effects in the isoscalar dipole modes of heavy nuclei are studied within a semiclassical model based on the solution of the Vlasov kinetic equation for finite Fermi systems with a moving surface. In order to clarify the role of dynamic surface effects we have considered an approximate solution, which takes into account only the part of the variation of the phase-space distribution function caused by the dynamic surface (the dynamic-surface approximation). It is shown that the dynamic surface effects have an essential influence on the features of the isoscalar dipole modes. The isoscalar dipole strength function has a two-resonance structure already in the dynamic-surface approximation, and the centroid energies of both the low-energy resonance and the high-energy resonance are close to corresponding centroid energies of exact strength function. Calculations of the velocity field in the dynamic-surface approximation show the vortex character of the low-energy isoscalar dipole resonance and the compression character of the high-energy one.