  The scattering of photons of x-ray energy off a Coulomb field in very forward
scattering region may be thought as the refraction effect due to the Coulomb
field. The cross section of the scattering can be computed from the photon
bending angle obtained in geometrical optics. Its dependence on the fine
structure constant is nonanalytic and softer than would the box diagrams of
Delbruck scattering suggest. The refractive scattering is a nonlocal effect
occurring over the distance scale of the impact parameter, and therefore may
not be described by the single-box diagrams. We suggest that the scattering
cross section is a consequence of the sum of the asymptotic series of the
multi-box diagrams.
