Variational calculation of the on- and off-shellTmatrix

The use of a Schwinger-type variational principle for the evaluation of the two-body $T$ matrix $T(p^{\prime },p,E)$ is shown to be an efficient and accurate method both on and off the energy shell. Using standard trial functions all of the matrix elements for the Reid soft-core interaction can be determined by simple recursion relations, and the evaluation of the $T$ matrix is reduced to solving a set of simultaneous equations.