The binding energies of the lowest isospin singlet ($J^{\pi }=1^{+}$) and triplet ($J^{\pi }=0^{+}$) states of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ are calculated on a multichannel three-body model in which the internal structure of the $\alpha$ particle is approximately represented by a two-state system. The $n-\alpha$ interaction is given by a two-channel $l$-dependent potential that is obtained by fitting low-energy scattering data. The $\mathrm{np}$ interaction is taken to be the Pease-Feshbach potential.

The Faddeev equations are generalized to allow spin and internal structure of the particles and are solved in the separable $t$-matrix approximation for bound-state energies. The results obtained are in good agreement with experiments and the effect of the $\alpha$ internal structure is discussed.

• Received 9 November 1972

DOI:https://doi.org/10.1103/PhysRevC.7.1329