3α-cluster structure of the 0⁺ states in ¹²C and the effective α‐α interactions

The 0⁺ states of ¹²C are considered within the framework of the microscopic three-α-cluster model. The main attention is paid to accurate calculation of the width of the extremely narrow near-threshold 0₂⁺ state which plays a key role in stellar nucleosynthesis. It is shown that the 0₂⁺-state decays by means of the sequential mechanism ¹²C→α+⁸Be→3α. Calculations are performed for a number of effective α‐α potentials which are chosen to reproduce both energy and width of ⁸Be. The parameters of the additional three-body potential are chosen to fix both the ground and excited state energies at the experimental values. The dependence of the width on the parameters of the effective α‐α potential is studied in order to impose restrictions on the potentials.