Loosely bound three-body nuclear systems in the J-matrix approach

We discuss the extension of the oscillator-basis J-matrix formalism on the case of true A-body scattering. The formalism is applied to loosely bound ¹¹Li and ⁶He nuclei within three-body cluster models ⁹Li+n+n and α+n+n. The J-matrix formalism is used not only for the calculation of the three-body continuum spectrum wave functions but also for the calculation of the S-matrix poles associated with the ¹¹Li and ⁶He ground states to improve the description of the binding energies and ground state properties. The effect of the phase equivalent transformation of the n-α interaction on the properties of the ⁶He nucleus is examined.