1992 Fiscal Year Final Research Report Summary
Studies of nuclear superdeformed states based on the microscopic theory
| Project/Area Number |
03640260
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
核・宇宙線・素粒子
|
|---|
| Research Institution | Saitama University |
|---|
Principal Investigator |
TANABE Kosai Saitama University, College of Liberal Arts, Professor, 教養部, 教授 (00008905)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
YOSHINAGA Naotaka Saitama University, College of Liberal Arts, Associate Professor, 教養部, 助教授 (00192427)
|
|---|
| Project Period (FY) |
1991 – 1992
|
| Keywords | Collective motion / High-spin states / Superdeformation / Hartree-Fock-Bogoliubov (HFB) approximation / Random phase approximation (RPA) / Chaos / Level statistics / Giant dipole resonance |
|---|
| Research Abstract |
Nuclear collective (vibrational and rotational) excitations are analyzed by applying the microscopic formalism, which composes these collective states directly from single-particle degrees of freedom and microscopic interactions among constituents. Our main results are as follows: (1) Since our attempt to describe superdeformed states in terms of the self-consistent solution to cranking HFB equation has been successful (already published), physical properties of giant dipole resonances (GDR) built on those superdeformed stats are analyzed. The RPA formalism at finite temperature is applied to calculate strength distribution, resonance width, asymmetry parameter of gamma-ray angular distribution from GDR etc. and the results are compered with those for normal-deformed states (ground band). Especially it is predicted that the critical gamma-ray energy, at which the asymmetry parameter a_2(E_<gamma>) changes its sign from negative to positive, becomes lower by about 3MeV in comparison wit
… More
h normal-deformed states in case of ^<132>Ce. This will provide important informations of deformation. Furthermore, we studied thermal fluctuations of macroscopic physical quantities in the framework of the microscopic formalism with constraints for those (in press). (2) Quantum signature of chaos was investigated for a classically pseudo-integrable system. It is found that the square type billiard with a zero size scattering point in the center is an example which partially contradicts the hypotheis (Wigner distribution for chaotic system and Poisson for integrable system) with respect to the level statistics (published in part, submitted in part). (3)Employing the Ginocchio model, we examined the collectivity and chaoticity. With the model we explained the experimental evidence that the lighter nuclei are more chaotic compared to the heavier ones (submitted for publication). (4)The interacting boson model with g-bosons is applied to the low-lying positive and negative parity states of the Ra isotopes. It is shown that the phase transition from the spherical to deformed shape is well described and it is essential to include g-bosons for reproducing strong E1 transitions. Furthermore, the lower spin negative parity states are understood in terms of the quadrupole deformation plus one octuple phonon picture (in press). Less
|
