DESCRIPTION OF THE EVEN TIN ISOTOPES IN A MIXING SHELL-MODEL AND IBA MODEL

Abstract

The positive parity energy levels of even Sn-108-124 isotopes are studied in terms of a mixing of shell model and interacting boson approximation model. In the calculation, the basis states consist of a pure boson configuration and N-B-1 bosons plus a fermion pair configuration, where N-B is the valence boson number outside the closed shell. The fermions are allowed to excite to the s(1/2), d(3/2), d(5/2), g(7/2) and h(11/2) single particle orbitals. The interaction Hamiltonian contains three parts: pure boson Hamiltonian, pure fermion Hamiltonian and boson-fermion mixing Hamiltonian. The calculated energy levels are compared with the observed data. The wavefunctions are used to calculate B(E2) values. It is found that the calculated energy spectra and B(E2) values agree reasonably well with the experimental values.