Toshimi Sakuda

Microscopic Study of Coexistence of Alpha-Cluster and Shell-Model Structure in the 40Ca-44Ti Region

The structure of the nuclei in the mass range 40 ≤ A ≤ 44 is investigated by the microscopic α + core orthogonality condition model. The energy spectra, electromagnetic transitions and α-spectroscopic factors are calculated. The calculated properties are in good overall agreement with the available experimental data. It is shown that the α-cluster states yield similar rotational bands which are characterized by the weak coupling feature and parity-doublet. The observed E2 intra-band transitions in the cluster bands, which show strong enhancement, and other transitions are systematically reproduced by the model. The model also gives a good account for enhancement and spreading of the α-spectroscopic factors. It is discussed that the coexistence and interference of α-cluster states and shellmodel states are important for understanding these features of the nuclei.

Coexistence of α-clustering and shell structure in40Ca

The energy spectrum and α-spectroscopic factors of40Ca are calculated by using an α+36Ar orthogonality condition model. Overall agreement is obtained with the experimental data. The model successfully produces the parity-doubletKπ=O+ and O− α+36Ar cluster bands. It is shown that the coexistence and interference of α-cluster states and shell-model states are indispensable to understand the structure of40Ca.The energy spectrum and α-spectroscopic factors of 40Ca are calculated by using an α + 36Ar orthogonality condition model. Overall agreement is obtained with the experimental data. The model successfully produces the parity-doublet K π =0+ and 0− α + 36Ar cluster bands. It is shown that the coexistence and interference of α-cluster states and shell-model states are indispensable to understand the structure of 40Ca.

Superdeformed Bands and α-Cluster States in A~40 Nuclei

T. Sakuda and S. Ohkubo Department of Physics, University of Miyazaki, Miyazaki 889-2192, Japan a Department of Applied Science and Environment, University of Kochi, Kochi 780-8515, Japan b Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan sakuda@cc.miyazaki-u.ac.jp The investigation of superdeformed (SD) rotational bands in Ar−Cr nuclei has received considerable attention. The collective aspects of these SD bands are particularly interesting subjects for nuclear structure studies. We have performed the α−cluster model calculations for the nuclei in this region and have shown that the observed energy spectra and E2 transitions are reproduced with good coincidence [1]. Figure 1 shows the experimental candidates for the α-cluster bands. The dotted and dashed lines connect the band heads of α-nh and 2α-mh cluster bands, respectively. The SD bands are also indicated by label SD. Our purpose is to clarify the relationship between the SD bands and 2α-cluster structure. The nucleus V provides the first link in the chain of 2α-mh cluster states in A=44−48 nuclei. Figure 2 shows the experimental positive-parity SD band of V [2], which shows fine collectivity. The investigation of the V using the 2α+K OCM is in progress and will be reported. [1] T. Sakuda and S. Ohkubo, Phys. Rev. C49, 149(1994); C51, 586(1995); C57, 1184(1998); Prog.Theor. Phys. Suppl. No.132, 103(1998); Phys. At. Nucl. 65, 703(2002); Nucl. Phys. A712, 59(2002); Nucl. Phys. A744, 77(2004). [2] F. Brandolini et al., Nucl. Phys. A693, 517(2001).