Microscopic Description of 8Li and 8B Nuclei Within a Three-Cluster Model
The theoretical analysis of structures of the bound and resonance states in 8Li and 8B nuclei is performed within a three-cluster microscopic model. In the framework of this model, 8Li and 8B nuclei are considered as three-cluster configurations 4He +3 H + n and 4He +3 He + p, respectively. A distinguished peculiarity of the model is that it allows us to consider the polarizability of weakly bound nuclei such as 7Li composed of an alpha particle and a triton or 7Be composed of an alpha particle and 3He. Gaussian and oscillator bases are used to expand the three-cluster wave function and to represent the many-channel Schr¨odinger equation in a matrix form. The main attention of the present study is paid to the effects of cluster polarization on the spectrum of bound and resonance states of 8Li and 8B and on the elastic and inelastic n +7Li and p +7Be scattering. It is shown that the cluster polarization has a great impact on parameters of the bound and resonance states in 8Li and 8B. For instance, it decreases the energy of resonance states by 0.7–2.0 MeV and increases their lifetime by more than three times. The roles of spin-orbital and Coulomb interactions in the formation of the spectrum of excited states in nuclei 8Li and 8B are studied in detail. In particular, it is found out that the Coulomb forces shift up the energy of resonance states in 8B with respect to the position of corresponding resonance states in 8Li and increases their widths.
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