Shota Suekane

Basic Rotational Band and Band Mixing in the Cranking Model

A new method is proposed in order to avoid the strange behaviour of the solution of the HFBC model in the band crossing region. For this purpose, the intrinsic states in a rotating nucleus are defined by excluding the interaction between basic rotational bands from the original cranked Hamiltonian, which are defined in the text. The basic rotational bands are constructed from the intrinsic states by using the condition of the angular momentum constraint and cross each other without mixing of the intrinsic states caused by rotation. The real rotational band bearing all of the effects of rotation is obtained by diagonalizing the Hamiltonian of the particle-rotor model rotating about the x-axis by using the states with the same angular momentum of the basic rotational bands. In the diagonalization, the basic zeroquasiparticle band and the lowest basic one-quasiparticle one-quasihole band are used. The resulting yrast band shows clearly the backbending.

OCTUPOLE TYPE DEFORMATION OF NUCLEAR SURFACE

The shell structure dependence of the surface rigidity to nuclear octupole type deformation is examined. In order to calculate the energy change due to octupole type deformation, a coordinate transformation which transforms a deformed surface into a spherical one is introduced. The results of the calculations are in good agreement with the trend of experimental data suggested by low lying odd parity states of even-even nuclei and display a characteristic shell structure dependence as well as quadrupole type deformation. According to the deformed potential model, it is shown that octupole type deformations are closely connected with quadrupole type deformations. This fact may play an important role in determining the spin values of low lying odd parity states of even-even nuclei and in understanding a mechanism of asymmetric fission. (auth)

The Magnetic Octupole Moments of Nuclei

The magnetic octupole moment !J of the nucleus is discussed on the basis of the shell and collective models. In the strong coupling case of the collective model, !2 becomes smaller than the shell model tuult because of the quenching of the moment along the symmetry axis of the deformed core. This fact is in agreement with experimental data (for Ga71, 73, In115, and Jl27) available at present.

The First-Order E2 Core Polarization Charge of 41Ca in Woods-Saxon Shell Model

41 Ca is calculated in the first-order perturbation theory by using the wave functions of a Woods-Saxon potential and compared with the results of harmonic oscillator potential. The contributions from the particle-hole excitations to continuum particle states, which constitute the major part of the excitations, are calculated explicitly. The resultant first-order core polarization charge in the Woods-Saxon shell model with a t-function type effective interaction 0.283e is smaller than the one of the harmonic oscillator shell model 0.3lle. The effects of the continuum states are discussed in comparison with the harmonic oscillator shell model.

Stability of Axially Asymmetric Nuclear Deformation

The gamma stability of axially asymmetric nuclear deformation is investigated on the basis of the generalized collective model. It is possible in the vibrational region to make the nonaxial deformation stable for the ground state, but it is necessary in this formalism to introduce a very strong potential to make the axially asymmetric shape stable in the rotational region.