SYSTEMATICS OF SUPERDEFORMATION FROM A~8 TO A~248

The systematics of superdeformation (∈≈0.6) is studied throughout the mass regions from A~8 to the fission isomers with A~242, including the recently observed superdeformed nuclei with A~152 and ~192. Strong shell effects are calculated which are described in a shell energy landscape in terms of valleys of stability which proceed from oblate through spherical to normal-deformed (∈≈0.25–0.3) and on to superdeformed and hyperdeformed (∈≈0.86) shapes with increasing nucleon number. Local minima in these valleys are calculated for prolate nuclei with 4, 10, 16, 28–32, 40–44, 60–66, 80–86, 110–116 and 140–150 neutrons and/or protons when the ratio of the major to minor axes is ≈ 2:1 and the deformation ∈≈0.6. Although the local minima represent the regions of greatest stability, the shell energy valleys should be viewed as more or less continuous structures in which a variety of different deformations can occur. Other local minima in the valleys of the shell energy landscape are observed for oblate (∈≈−0.75) and hyperdeformed nuclei. When shell effects are added to the liquid-drop potential in the Nilsson-Strutinsky formalism, spherical and normal deformation shapes tend to predominate. However, superdeformed, oblate and hyperdeformed shapes are also predicted. In the case of superdeformed nuclei, shell effects predominate over the liquid-drop potential for the light nuclei creating superdeformed ground states. In intermediate-mass nuclei, the liquid-drop potential predominates and superdeformation is only observed at fairly high energy and at high spins where the superdeformation is stabilized. In the heaviest nuclei, the combined effect of the Coulomb potential and the fissionability of the liquid drop causes the potential to reach a maximum at ∈≈0.6. The shell effect then produces a second minimum 2–3 MeV above the ground state with its coexisting spectroscopy. Existing experimental data throughout the nuclear periodic table are shown to be in remarkable agreement with theoretical expectations. Predictions of new regions of superdeformation are presented.