Masaaki Kimura

Breaking of the Neutron Magic Number N=20 in 32Mg and 30Ne and Its Possible Relation to the Cluster Structure

The neutron-rich nuclei 3 2 Mg and 3 0 Ne are studied using a new version of antisymmetrized molecular dynamics (AMD). Due to the use of a deformed Gaussian as the single particle wave packet, the description of the deformation properties of Mg isotopes is drastically improved, and l.s force is accounted for more largely and sufficiently. After the angular momentum projection, 3 2 Mg and 3 0 Ne have deformed ground states, and the experimental data for 3 2 Mg are reproduced with reasonable accuracy. The deformation of the mean field is found to be essential to describe these nuclei. The ground states of these nuclei have neutron 2p2h structure. In 3 0 Ne, the cluster-like and the mean-field-like structures coexist. The ground state of 3 2 Mg has a mean-field-like structure. In the vicinity of the ground state, this nucleus is expected to have excited states with cluster-like structure that possesses the neutron 4p4h configuration.

Deformation and Clustering in Even-Z Nuclei Up to Mg Studied Using AMD with the Gogny Force

Employing the Gogny force as an effective force, we study the ground state properties of light nuclei using antisymmetrized molecular dynamics (AMD). In a previous paper, we discussed the nuclear binding energies and nuclear radii of He, Be, C, O, Ne and Mg isotopes. In this paper, we mainly consider the deformation properties and the clustering nature of these isotopes. By comparing the calculated results with the AMD results by use of the Skyrme-III (SIII) force, we investigated the differences and similarities between the SIII force and the Gogny force. We find that the Gogny force yields rather better binding energy and larger deformation than the SIII force. We carry out the parity-projected calculations. Parity projection enhances the parity-violating deformation and the cluster structure of certain nuclei. Shape of the deformation energy surface is also changed by parity projection. This causes a competition between the mean-field-like structure and the cluster-like structure. A modified version of AMD, which employs deformed Gaussian wave packets instead of spherical ones, is shown to give large quadrupole moments in the case of Mg isotopes.

Breaking of the Magic Number N = 20 Studied with the New Version of AMD

The neutron-rich nuclei 3 2 Mg and 3 0 Ne are studied using a new version of antisymmetrized molecular dynamics (AMD). After the angular-momentum projection, 3 2 Mg and 3 0 Ne have largely deformed ground states, and theexperimental data for 3 2 Mg are reproduced with reasonable accuracy. The ground states of these nuclei have neutron 2p2h structure. We also have studied the negative-parity states of these nuclei. Their lowest negative-parity states which have spin-parity 1 - have quite small excitation energies compared to stable N = 20 isotones. By using the Gogny force, their excitation energies have calculated to be 2.4 MeV for 3 0 Ne and 2.3 MeV for 3 2 Mg and these 1 - states have neutron 3p3h structure.

Coexistence of Cluster Structure and Mean‐field‐type Structure in Medium‐weight Nuclei

We have studied the coexistence of cluster structure and mean‐field‐type structure in 20Ne and 40Ca using Antisymmetrized Molecular Dynamics (AMD) + Generator Coordinate Method (GCM). By energy variation with new constraint for clustering, we calculate cluster structure wave function. Superposing cluster structure wave functions and mean‐field‐type structure wave function, we found that 8Be‐12C, α‐36Ar and 12C‐28Si cluster structure are important components of Kπu2009=u200903+ band of 20Ne, that of normal deformed band of 40Ca and that of super deformed band of 40Ca, respectively.