Gamma transitions with \( \lambda=0 \) are forbidden because the photon must carry off at least one unit of angular momentum. The \( e_{q} \) are the electric charges for the proton and neutron in units of \( e \). For the free-nucleon charge we would take \( e_{p}=1 \) and \( e_{n}=0 \), for the proton and neutron, respectively. Although the bare operator acts upon the protons, we will keep the general expression in terms of \( e_{q} \) in order to incorporate the effective charges for the proton and neutron, which represent the center-of-mass corrections and the average effects of the renormalization from wavefunction admixtures outside the model space.