Extraction of the ratio of the N∗ (1535) electromagnetic helicity amplitudes from eta photoproduction off neutrons and protons

Using the recent precise measurements of eta photoproduction in proton and deuteron targets, we extract the ratio of the helicity amplitudes A12nA12p, for the excitation of N∗ (1535), in the effective Lagrangian approach. It is fairly model-independent, free from the final-state interaction effects, and negative as predicted by the quark models. We stress the importance of polarization observables in further elucidation of the N∗ (1520) photoexcitation amplitudes.