Estimate of the Importance of Retardation in Nuclear Binding

A potential form alternate to the customary Yukawa form is deduced. This nonlocal potential incorporates retardation of the meson and nucleon normalization factors. A phenomenological potential patterned after the Reid soft-core potential is constructed. This new phenomenological potential is compared with the Reid potential off the energy shell. The off-shell changes lead to a decrease in the binding energy of nuclear matter of 1.5 MeV/particle in the ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}-{}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}$ state and an increase of 0.1 MeV/particle in the ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ state.