MICROSCOPIC DESCRIPTION OF 8Li AND 8B NUCLEI WITHIN A THREE-CLUSTER MODEL

The theoretical analysis of structures of the bound and resonance states in Li-8 and B-8 nuclei is performed within a three-cluster microscopic model. In the framework of this model, Li-8 and B-8 nuclei are considered as three-cluster configurations He-4 + H-3 +n and He-4 + He-3 + p, respectively. A distinguished peculiarity of the model is that it allows us to consider the polarizability of weakly bound nuclei such as Li-7 composed of an alpha particle and a triton or Be-7 composed of an alpha particle and He-3. Gaussian and oscillator bases are used to expand the three-cluster wave function and to represent the many-channel Schrodinger 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 Li-8 and B-8 and on the elastic and inelastic n + Li-7 and p + Be-7 scattering. It is shown that the cluster polarization has a great impact on parameters of the bound and resonance states in Li-8 and B-8. 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 Li-8 and B-8 are studied in detail. In particular, it is found out that the Coulomb forces shift up the energy of resonance states in B-8 with respect to the position of corresponding resonance states in Li-8 and increases their widths.