  In scattering theory, the squared relative wave function $|\phi({\bf q},{\bf
r})|^2$ is often interpreted as a weight, due to final-state interactions,
describing the probability enhancement for emission with asymptotic relative
momentum $q$. An equivalence relation also links the integral of the squared
wave function over all coordinate space to the density of states. This
relation, which plays an important role in understanding two-particle
correlation phenomenology, is altered for the case where the potential is
energy dependent, as is assumed in various forms of reaction theory. Here, the
modification to the equivalence relation is derived, and it is shown that the
squared wave function should be augmented by a additional factor if it is to
represent the emission enhancement for final-state interactions. Examples with
relativistic vector interactions, e.g., the Coulomb interaction, are presented.
