Phase-shift calculation using continuum-discretized states

We present a method for calculating scattering phase shifts which utilizes continuum-discretized states obtained in a bound-state type calculation. The wrong asymptotic behavior of the discretized state is remedied by means of the Green's function formalism. Test examples confirm the accuracy of the method. The $\alpha+n$ scattering is described using realistic nucleon-nucleon potentials. The $3/2^-$ and $1/2^-$ phase shifts obtained in a single-channel calculation are too small in comparison with experiment. The $1/2^+$ phase shifts are in reasonable agreement with experiment, and gain contributions both from the tensor and central components of the nucleon-nucleon potential.