Photon Absorption in Nuclei and Vector-Meson Dominance

We show that in some applications of vector-meson dominance to photon reactions in nuclei the mass of the $\rho$ meson cannot be neglected at photon energies of current interest. Thus, in calculation of the photon absorption cross section in the optical-model approximation, the effect of the $\rho$ mass $m_{\rho }$ is important for photon energies $\omega \lesssim m_{\rho }^{}{}_{}{}^2{(\frac{R}{\sigma N)}}^{\frac{1}{2}}$, where $R$ and $N$ are the radius and density of the nucleus, and $\sigma$ is the total $\rho$-nucleon cross section.