Theoretical Research of Sof-dipole Resonances in Light Neutron-Rich Nuclei

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The purpose of this project is to obtain a theoretical conclusion about existence and observation of soft-dipole resonaces in ^6He and ^<11>Li whichare typical nuclei of light neutron rich nuclei. For this purpose, the following three problems were studied in these three years of 2000-2002 and desired results were successfully obtained :(1) Theoretical researches of soft-dipole resonances in three-body Coulomb breakup reactions. Using the complex scaling method, we developed a new theoretical framework to treat three-body breakup reactions. Applying this new method to ^6He and 11Li, we calculated the breakup cross sections where contributions from soft-dipole resonances are negligible.(2) Study of binding and excitation mechanisms by using an extended core+n+n model where internal degrees of freedom of the core cluster are taken into account. It was shown that the pairing correlations not only between valence neutrons but also between neutrons in the ^9Li core play an important role in the binding mechanism and a large amplitude of s-wave components.(3) Mechanism of appearance of s-wave anti-bound states. Analyses of s-wave anti-bound states in ^4He-n and ^9Li-n systems gave a clear relation between position of anti-bound poles and property of ^4He-n and ^9Li-npotentials.