Multichannel three-α model of ¹²C

A multichannel three-α model is constructed to calculate the ground and first excited state energies of ¹²C by assuming that the internal structure of the α-particle is approximately represented by a two-level system. The multichannel α-α potential is obtained by fitting the low-energy scattering data near the resonances. The Faddeev equations are generalized to allow the internal structure of the particles, and are solved in the separable t-matrix approximations for bound state energies. The results obtained are in good agreement with experiments and the effect of the α internal structure is discussed.