THE 4-ALPHA ORTHOGONALITY CONDITION MODEL FOR LOW-LYING O+ STATES OF O-16

The 4-alpha orthogonality condition model is studied by using the alpha-alpha potential to reproduce the alpha-alpha system and the phenomenological 3-alpha potential to reproduce binding energies of 3-alpha and 4-alpha systems. Analyzing solved 4-alpha wave functions of the five low-lying 0+ states corresponding to the observed levels of O-16, we discuss the coexistence of the shell structure of the ground state and C-12-alpha molecule-like structures of excited states. Comparing with results of the C-12 + alpha orthogonality condition model, we give a justification of the C-12 + alpha model.