Phase Transitions between Axisymmetric and Nonaxial Nuclear Shapes

摘要

Within the interacting-boson model, phase transitions between different nuclear shapes are considered in the space of three control parameters. Depending on the values of these parameters, the equilibrium shape of a nucleus can be spherical, axially deformed, or nonaxial. It is shown that the phase transition from an axisymmetric to a nonaxial deformation is a second-order phase transition. Within the Bohr–Mottelson model, an approximate solution is found that describes a nucleus in the vicinity of the critical point of a phase transition from a spherical to nonaxially deformed shape. The results obtained for the energies and E2-transition probabilities are close to experimental data for the ~(134)Ba nucleus.