The enhancement factor $\kappa$ in the electric dipole sum rule is calculated for $A=2, 4, 16$ nuclei. Accurate solutions of the coupled Hartree- Fock, Bethe-Goldstone, and Bethe-Faddeev equations have been used for different realistic $\mathrm{NN}$ potentials. The need for measurements of the total cross sections, especially for ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, is emphasized.

• Received 7 September 1978

DOI:https://doi.org/10.1103/PhysRevLett.41.1288