Cluster molecular structure in neutron-rich nuclei

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We investigated isovector excitations of nuclei via the (^7Li,^7Be) charge exchange reaction at 455 MeV. A ^7Li^<3+> beam was provided from the ring cyclotron of the Research Center for Nuclear Physics, Osaka University. Our research was focused on the molecular structure in neutron-rich nuclei and the (γ,n) cross section deduced with the (^7Li,^7Be) charge exchange reaction. We got tow main results. The (^7Li,^7Be) reaction can provide the spin-flip (ΔS=1) and spin-nonflip (ΔS=0) spectra by measuring the ^7Be particle in coincidence with the 0.43-MeV γ-ray of ^7Be.1. Tri-nucleon cluster structure in ^6He, ^6Li and ^6Be. The structure was found to be a molecular-like structure composed of tri-nucleon clusters of t and/or ^3He, which is a two-fermion system. The ^1P and ^3P resonances were assigned from the measured angular correlations of decay particles and the analysis of the spectral shape by using the Breit-Wigner formula.2. A new approach to the photodisintegration cross section deduced with the (^7Li,^7Be) charge exchange reaction. We applied the method to the ^2H(γ,n) and ^4He(γ,n) reaction. The former showed that the (^7Li,^7Be) ΔS=1 and ΔL=0 spectrum was successfully used to deduce the distribution of the B(M1) reduced matrix elements for the photodisintegration of deuteron from the analogous B(GT) distribution. The latter showed that the (^7Li,^7Be) ΔS=0 and ΔL=1 spectrum was successfully used to deduce the El photodisintegration cross section for the giant dipole resonance in ^4He.