Coulomb energies inS-shell nuclei and hypernuclei

We estimate the Coulomb energy component of the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-${}_{}{}^3{}_{}{}^{}\mathrm{H}$ binding energy difference, using the latest elastic electron scattering form factor data, to be 639±19 keV, in agreement with previous estimates. We estimate the Coulomb energy of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ to be 757±23 keV. We discuss the Coulomb energy contribution to the $\Lambda$ separation energy difference $B_{\Lambda }\left({}_{\Lambda }{}^4{}_{}{}^{}\mathrm{He}\right)-B_{\Lambda }\left({}_{\Lambda }{}^4{}_{}{}^{}\mathrm{H}\right)$.