Coexistence of shell structure and cluster structure in 20Ne

Abstract

The coexistence of a shell-model aspect and an α-cluster aspect in 20Ne is studied using a model space which is constructed by combining a (1s0d) 4 shell-model space and a microscopic 16O core plus α-cluster model space. A method is given for calculating matrix elements of one- and two-body operators between basis states of this model space. We assume a microscopic Hamiltonian which involves a two-body effective interaction consisting of central, L- S and Coulomb potentials. The states below the α-decay threshold are obtained by diagonalizing the Hamiltonian, while for those above the threshold, the α- 16O scattering phase shifts are calculated by solving a coupled scattering equation variationally under an appropriate boundary condition. Energy levels, reduced α-widths and B(E2) values are calculated and compared with experimental values. Three K π = 0 + bands built on 0 1 +(g.s.), 0 2 +(6.72 MeV) and 0 4 +(8.6 MeV) states and the first K π = 0 − band on the l 1 − state at 5.79 MeV are successfully described by the present model.