Octupole response and stability of spherical shape in heavy nuclei

• Published in: Nuclear physics. A 2003-11, Vol.727 (3), p.220-232
• Main Authors: Abrosimov, V.I., Davidovskaya, O.I., Dellafiore, A., Matera, F.
• Format: Article
• Language: English
• Subjects: Isoscalar octupole resonances; Octupole surface modes; Vlasov equation
• ISSN: 0375-9474
• DOI: 10.1016/j.nuclphysa.2003.08.014

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 1ℏ ω and 3ℏ ω regions, in excellent agreement with the quantum single-particle response. The collective fixed-surface response reproduces both the high- and low-energy octupole resonances, 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.