What are the advantages of a three body model with core excitation for 21Ne and 21Na? Original Research Article

21Ne and 21Na are well bound nuclei and there is a large amount of data available up to considerable excitation energy, and this imposes a severe test on the structure models. Preliminary results for the structure of these nuclei based on three body models (21Ne=16O+α+n and 21Na=16O+α+p) are presented. Three-body calculations without core excitation produce the positive parity states in fair agreement with experiment, while slightly overbinding the systems. As expected, these models fail to reproduce the low lying negative parity states, which are predicted by shell model to have mainly core excited configurations. As a first step we have included the 3– state of 16O in our model. Convergence issues will be discussed. Results suggest that more excited states may be required to describe the system.