Kiyoshi Katō

Five-body resonances of 8He using the complex scaling method

Abstract The 0 + states of 8He are studied in a five-body He 4 + n + n + n + n cluster model. Many-body resonances are treated on the correct boundary condition as Gamow states using the complex scaling method. The 0 2 + state of 8He is predicted as a five-body resonance in the excitation energy of 6.3 MeV with a width of 3.2 MeV, which mainly has a ( p 3 / 2 ) 2 ( p 1 / 2 ) 2 configuration. In this state, number of the 0 + neuron pair shows almost two, which is different from the ground state having a large amount of the 2 + pair component. The monopole transition of 8He from the ground state into the five-body unbound states is also evaluated. It is found that the He 7 + n component mostly exhausts the strength, while the 0 2 + contribution is negligible. The final states are dominated by He 6 + n + n , not He 4 + n + n + n + n . The results indicate the sequential breakup process of He 8 → He 7 + n → He 6 + n + n by the monopole excitation.

New description of the four-body breakup reaction

We present a novel method of smoothing discrete breakup cross sections calculated by the method of continuum-discretized coupled channels. The smoothing method based on the complex scaling method is tested with success for a {sup 58}Ni(d,pn) reaction at 80 MeV as an example of three-body breakup reactions and applied to a {sup 12}C({sup 6}He,nn {sup 4}He) reaction at 229.8 MeV as an example of four-body breakup reactions. Fast convergence of the breakup cross section with respect to extending the model space is confirmed. The method is also applied to {sup 12}C({sup 6}He,nn {sup 4}He) and {sup 208}Pb({sup 6}He,nn {sup 4}He) reactions at 240 MeV/A and compared with the experimental data.

Five-body resonances of 8C using the complex scaling method

We study the resonance spectroscopy of the proton-rich nucleus 8 Ci n theα + p + p + p + p cluster model. Many-body resonances are treated on the correct boundary condition as the Gamow states using the complex scaling method. We obtain the ground state of 8 C as a five-body resonance for the first time, which has dominantly the subclosed (p3/2) 4 configuration and agrees with the recent experiment for energy and decay width. We predict the second 0 + state with the excitation energy of 5.6 MeV, which corresponds to the 2p2h state from the ground state. We evaluate the occupation numbers of four valence-protons in the 8 C states and also the J π distribution of proton-pair numbers of the two 0 + states of 8 C. The ground state involves a large amount of the 2 + proton-pair fraction, while the excited 0 + state almost consists of two of the 0 + proton pairs, which can be understood from the (p3/2) 2 (p1/2) 2 configuration. We also discuss the mirror symmetry between 8 Ca nd 8 He with an α+four nucleon picture. It is found that the 0 + states retain the mirror symmetry well for the configuration properties of two nuclei.

Four-body resonances of 7B using the complex scaling method

Be[1]. The unstable nuclei can often be unbound statesbeyond the particle thresholds due to the weak bindingnature. The resonance spectroscopy of unbound statesbeyond the drip-line has also been developed experimen-tally. In addition to the energies and decay widths, theconfiguration properties are important to understand thestructures of the resonances. The spectroscopic factors(S-factors) give the useful information to know the con-figurations of extra nucleons in the resonances as wellas in the weakly bound states. It is also interesting tocompare the structures of resonances and weakly boundstates between proton-rich and neutron-rich sides, whichis related to the mirror symmetry in unstable nuclei.Recently, the experiment on

Tensor Force Effects on α-α Clustering of 8Be

The Brueckner theory is applied to the antisymmetrized molecular dynamics (AMD) of 8 Be with the aim of studying the clustering mechanism on the basis of the realistic nuclear force. The role of the tensor force in the clustering is investigated through the analysis of single-particle energies depending on the single-particle orbits, which change from onecenter atomic orbits to two-center molecular orbits with the development of the α-α cluster structure. The clustering is intensified by the suppression of the attractive tensor force role in the one-center atomic orbits in the shell model structure. Subject Index: 210, 211

Brueckner‐AMD Study of Light Nuclei

We applied the Brueckner theory to the Antisymmetrized Molecular Dynamics (AMD) and examined the reliability of the AMD calculations based on realistic nuclear interactions. In this method, the Bethe‐Goldstone equation in the Brueckner theory is solved for every nucleon pair described by wave packets of AMD, and the G‐matrix is calculated with single‐particle orbits in AMD self‐consistently. We apply this framework to not only α‐nuclei but also N≠Z nuclei with A∼10. It is confirmed that these results present the description of reasonable cluster structures and energy‐level schemes comparable with the experimental ones in light nuclei.

BRUECKNER-AMD STUDY OF LIGHT NUCLEI

We applied the Brueckner theory to the Antisymmetrized Molecular Dynamics (AMD), and show the reliability of the AMD calculations based on realistic nuclear interactions. Focusing our interest on a structure dependence of the tensor force, we investigate the α-α clusterization of 8Be.