Charge exchange in the final state of direct (γ, n) reactions

The two-step charge-exchange contribution coming from a direct (γ, p) reaction followed by a (p, n) transition due to isospin dependence of the optical-model potential is studied for photonuclear reactions. The charge-exchange mechanism appears to be substantial: its contribution is strongly dependent on the rather uncertain isospin term in the phenomenological optical-model potential, but is still insufficient to make the size of the (γ, n) cross section comparable with the (γ, p) one as found experimentally