Numerical Study of a Separable Approximation to a Local Potential

A separable approximation to a local square-well potential is examined. For $s$-wave scattering it is shown that a rank-2 separable potential can be constructed which fits the square-well phase shifts below 300 MeV, and also reproduces the off-shell $T$-matrix elements over the entire region where the $T$ matrix is, itself, appreciable.