Alpha-like four-body correlations and molecule-like structure in nuclei in the fp-sell region

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1.It has been shown that the structure of ^<44>Ti including the alpha-spectroscopic factors is consistently understood in an alpha-cluster model. The K = 0^+ band starting at 1.9 MeV is explained by the alpha-cluster model in which excitation of the core is taken into account.2. The predicted K = 0^- band in ^<40>Ca has been observed in the ^<36>Ar (^6Li, d) ^<40>Ca reaction and it was found the alpha-spectroscopic factors of the band are fragmented. By taking a semimicroscopic alpha+^<36>Ar orthogonality condition model which takes into account the excitation of the core, we could reproduce well the experimental energy levels, spectroscopic factors and B (E2) values. It was also found that the model reproduces not only the cluster states but also the shell-model like states simultaneously. The mechanism of coexistence of cluster and shell structure is revealed.3. The structure of ^<42>Ca was studied in the alpha+^<38>Ar orthogonality condition model. Experimental energy levels and B ( … More E2) values are well reproduced by the model. It is found that cluster and shell structure also coexist in ^<42>Ca.4.alpha-clustering aspects are also studied in the latter part of the sd-shell from the viewpoint of unification of bound and scattering states. Through the study of alpha-cluster structure of ^<38>Ar, it is suggested that weak-coupling and alpha-cluster structure persist in this region.5. Extension of the viewpoint of molecule-like structure in nuclei to much heavier region has been done. It was found that alpha-scattering from ^<90>Zr and ^<208>Pb and the ground band of the composite system ^<94>Mo and ^<212>Po are simultaneously reproduced well, respectively, by taking a double folding model. This shows that the ground band of these nuclei is understood from the alpha-cluster viewpoint. Spectroscopic properties and band structure of ^<94>Mo and ^<212>Po were investigated. The large alpha-decay width of the ground state of ^<212>Po is reproduced well by the cluster model.To summarize, if is found theoretically and experimentally that alpha-cluster structure persists in the fp-shell region. It is also discussed that alpha-cluster picture persists in much heavier nuclei such as ^<94>Mo and ^<212>Po, and possibly throughout the periodic table. Less