Kenichi Matsuyanagi

High-spin isomers in Po, At and Rn in the deformed independent particle model

Abstract The isomeric states in Po, At and Rn isotopes are described as independent particle states in a deformed potential which is symmetric with respect to the direction of the angular momentum. The known parts of the yrast lines of these nuclei are found to be well described by the model. In particular all observed isomeric states are reproduced as “traps”. The variation of the shape along the yrast line is studied. In most of the nuclei considered a gradual rise of oblate deformation takes place. This can be understood from simple qualitative considerations. The relation of the present approach to a description within the spherical shell model with residual interactions is discussed.

Symmetry-unrestricted Skyrme–Hartree–Fock–Bogoliubov calculations for exotic shapes in N=Z nuclei from 64Ge to 84Mo

Abstract By performing fully 3D symmetry-unrestricted Skyrme–Hartree–Fock–Bogoliubov calculations, we discuss shape coexistence and possibility of exotic deformations simultaneously breaking the reflection and axial symmetries in proton-rich N=Z nuclei: 64Ge, 68Se, 72Kr, 76Sr, 80Zr and 84Mo. Results of calculation indicate that the oblate ground state of 68Se is extremely soft against the Y 33 triangular deformation, and that the low-lying spherical minimum coexisting with the prolate ground state in 80Zr is extremely soft against the Y 32 tetrahedral deformation.

Interplay of Pairing and Intrinsic Modes of Excitation in Nuclei. I : Transcription of Nucleon System into Ideal Boson-Quasi-Particle Space

A new method treating the interplay of pairing and intrinsic modes of excitation is proposed. In this method, the pairing mode associated with the J=O-coupled nucleon pairs is represented by pairing bosons and the intrinsic mode characterized by the seniority quantum number is explicitly treated by ideal quasi-particle operators. We obtain a closed expression of the single-nucleon operator in terms of pairing bosons and ideal quasi-particles. As a simple illustration, the superconducting system is treated by introducing the coherent state of pairing bosons and the relation to the Bogoliubov transformation is discussed. The relation between this method and the· canonical transformation method with auxiliary variables is also clarified.

Microscopic structure of high-spin vibrational excitations in superdeformed {sup 190,192,194}Hg

Microscopic calculations based on the cranked shell model extended by the random-phase-approximation are performed to investigate the quadrupole and octupole correlations for excited superdeformed bands in {sup 190}Hg, {sup 192}Hg, and {sup 194}Hg. The {ital K}=2 octupole vibrations are predicted to be the lowest excitation modes at zero rotational frequency. At finite frequency, however, the interplay between rotation and vibrations produces different effects depending on neutron number: The lowest octupole phonon is rotationally aligned in {sup 190}Hg, is crossed by the aligned two-quasiparticle bands in {sup 192}Hg, and retains the {ital K}=2 octupole vibrational character up to the highest frequency in {sup 194}Hg. The {gamma} vibrations are predicted to be higher in energy and less collective than the octupole vibrations. From a comparison with the experimental dynamic moments of inertia, a new interpretation of the observed excited bands invoking the {ital K}=2 octupole vibrations is proposed, which suggests those octupole vibrations may be prevalent in superdeformed Hg nuclei. {copyright} {ital 1996 The American Physical Society.}

High-spin yrast structure of 32S suggested by symmetry-unrestricted, cranked Hartree–Fock calculations

The high-spin yrast structure of 32 S is investigated by means of the cranked Skyrme‐Hartree‐ Fock method in the three-dimensional Cartesian-mesh representation without imposing restrictions on spatial symmetries. The result suggests that (1) a crossover from the superdeformed to the hyperdeformed-like configurations takes place on the yrast line at angular momentum I’ 24, which corresponds to the “band termination” point in the cranked harmonic-oscillator model, and (2) nonaxial octupole deformations of the Y31 type play an important role in the yrast states in the range 56I6 13.

Time-dependent density-functional description of nuclear dynamics

The basic concepts and recent developments in the time-dependent density-functional theory (TDDFT) for describing nuclear dynamics at low energy are presented. The symmetry breaking is inherent in nuclear energy density functionals, which provides a practical description of important correlations at the ground state. Properties of elementary modes of excitation are strongly influenced by the symmetry breaking and can be studied with TDDFT. In particular, a number of recent developments in the linear response calculation have demonstrated their usefulness in the description of collective modes of excitation in nuclei. Unrestricted real-time calculations have also become available in recent years, with new developments for quantitative description of nuclear collision phenomena. There are, however, limitations in the real-time approach; for instance, it cannot describe the many-body quantum tunneling. Thus, the quantum fluctuations associated with slow collective motions are explicitly treated assuming that time evolution of densities is determined by a few collective coordinates and momenta. The concept of collective submanifold is introduced in the phase space associated with the TDDFT and used to quantize the collective dynamics. Selected applications are presented to demonstrate the usefulness and quality of the new approaches. Finally, conceptual differences between nuclear and electronic TDDFT are discussed, with some recent applications to studies of electron dynamics in the linear response and under a strong laser field.

Theory of Collective Excitations in Spherical Odd-Mass Nuclei. III Electromagnetic Properties of the Anomalous Coupling States

Various electromagnetic properties of the anomalous coupling states with spin (j-1) are shown to be well explained by the new viewpoint of the dressed n-quasi-particle modes proposed in a previous paper. In this point of view, the anomalous coupling collective states with spin (j -1) are considered as the dressed three-quasi-particle modes, which are regarded as a kind of elementary excitation modes in odd-mass nuclei. The effects of couplings between dressed three-quasi-particle modes and one-quasi-particle mode~ are also discussed in this connection, including those with spin j, (j-1) and (j-2).

Cranked Skyrme–Hartree–Fock calculation for superdeformed and hyperdeformed rotational bands in N=Z nuclei from 32S to 48Cr

Abstract With the use of the symmetry-unrestricted cranked Skyrme–Hartree–Fock method in the three-dimensional coordinate-mesh representation, we have carried out a systematic theoretical search for the superdeformed and hyperdeformed rotational bands in the mass A =30–50 region. Along the N = Z line, we have found superdeformed solutions in 32 S, 36 Ar, 40 Ca, 44 Ti, and hyperdeformed solutions in 36 Ar, 40 Ca, 44 Ti, 48 Cr. The superdeformed band in 40 Ca is found to be extremely soft against both the axially symmetric ( Y 30 ) and asymmetric ( Y 31 ) octupole deformations. An interesting role of symmetry breaking in the mean field is pointed out.

Wobbling motion in atomic nuclei with positive gamma shapes

The three moments of inertia associated with the wobbling mode built on the superdeformed states in

Nuclear field theory treatment of complex nuclear spectra

{}^{163}\mathrm{Lu}