We derive expressions for the low energy behavior of the multipole amplitudes of ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(γ,n${)}^1$H. Our results follow from the relativistic treatment of the long wavelength limit for the photon. We enforce unitarity, point out the incompatibility of this with gauge invariance, and suggest a possible solution. We discuss in some detail the forward differential cross section.

• Received 10 May 1989

DOI:https://doi.org/10.1103/PhysRevC.42.846