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Octupole response and stability of spherical shape in heavy nuclei

V. I. Abrosimov·O. I. Davidovskaya·A. Dellafiore·F. Matera
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Abstract

The isoscalar octupole response of a heavy spherical nucleus is analyzed in a semiclassical model based on the linearized Vlasov equation. The octupole strength function is evaluated with different degrees of approximation. The zero-order fixed-surface response displays a remarkable concentration of strength in the $1\hbarω$ and $3\hbarω$ regions, in excellent agreement with the quantum single-particle response. The collective fixed-surface response reproduces both the high- and low-energy octupole rsonances, but not the low-lying $3^{-}$ collective states, while the moving-surface response function gives a good qualitative description of all the main features of the octupole response in heavy nuclei. The role of triangular nucleon orbits, that have been related to a possible instability of the spherical shape with respect to octupole-type deformations, is discussed within this model. It is found that, rather than creating instability, the triangular trajectories are the only classical orbits contributing to the damping of low-energy octupole excitations.

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V. I. Abrosimov, O. I. Davidovskaya, A. Dellafiore, F. Matera. 2003-07-10. Octupole response and stability of spherical shape in heavy nuclei. https://doi.org/10.1016/j.nuclphysa.2003.08.014

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