A Sobiczewski

On the nuclear structure and stability of heavy and superheavy elements

Abstract Nuclear potential energy surfaces as a function of deformations are calculated on the basis of a modified oscillator model. In particular, quadrupole ( P 2 ) and hexadecapole ( P 4 ) deformations are considered. The average behavior of the surface is normalized to that of a liquid drop through the employment of a generalized Strutinsky prescription. In this way a synthesis of the single-particle model and the liquid-drop model is obtained. Lowest minima in the potential energy surfaces give the ground state masses and distortions. These results compare extremely well with experimental data. Spontaneous fission half-lives are also obtained. The inertial parameters associated with fission barrier penetration are derived empirically as well as by a microscopic model. Shape (fission) isomeric states are also found. Their N and Z dependence in the present model are discussed and results tabulated. The calculations are extended to the predicted superheavy region around Z = 114 and N = 184. The total overall stability with respect to alpha and beta decay, and spontaneous fission is found to be most favorable in the vicinity of Z = 110 and N = 184. Detailed diagrams and tables are exhibited.

On the spontaneous fission of nuclei with Z near 114 and N near 184

Abstract Theoretical calculations of the potential energy surface as a function of quadrupole and hexadecapole distortion parameters are reported for super-heavy nuclei with Z near 114 and N near 184. Estimates of spontaneous fission half-lives indicate a sizable island of relative stability in the vicinity of these closed-shell nucleon numbers.

Microscopic calculations of the inertial mass parameter for fissioning nuclei

Abstract Inertia mass parameter B in a fissioning nucleus is calculated. The method of calculation is based on the assumption of adiabatic collective motion in the fission degree of freedom. Resulting values for B are 4 to 11 times larger than those obtained from the liquid-drop model estimates. It turns out that the inertial parameter increases almost linearly with nuclear deformation. It also appears to be a sensitive function of the pairing force strength. Rough estimates of the coupling between quadrupole and hexadecapole modes seem to indicate that it may modify considerably the obtained results. The calculations are extended to the predicted superheavy region connected with Z ≈ 114.

On the stable octupole deformation of nuclei

Abstract The potential energy of nuclei in the Ra region is studied by a modified macroscopic-microscopic method which accounts for the consistency condition between the macroscopic and microscopic parts of the energy. A stable octupole deformation is obtained for a number of nuclei. The lowest Kπ=0− states are interpreted as being associated with this deformation.

Hexadecapole equilibrium distortions of nuclei

Abstract Theoretical calculations of nuclear deformed shell model equilibrium shapes in the rare earth and actinide regions have yielded hexadecapole distortions in good agreement with recent experimental shapes determined from (α, α′) scattering analysis. Pairing, Coulomb and polarisation effects are included in the calculations.

Coupled octupole and quadrupole vibrations of nuclei around radium

Abstract Consequences of the octupole instability of an even-even nucleus for its collective properties are studied. The energies of the lowest collective states and the electromagnetic transitions between them are considered. The results suggest a rather strong octupole instability for some nuclei in the radium region.