  We consider the long-time behavior of the massless Dirac equation coupled to
a Coulomb potential. For nice enough initial data, we find a joint asymptotic
expansion for solutions near the null and future infinities and characterize
explicitly the decay rates seen in the expansion.
  This paper can be viewed as a successor to previous work on asymptotic
expansions for the radiation field. The key new elements are propagation
estimates near the singularity of the potential, building on work of the first
author with Wunsch and an explicit calculation with hypergeometric functions to
determine the rates of decay.
