Simple analytical representation for Delbruck scattering amplitudes at high energies

We use a new representation for the semiclassical Green's function of the Dirac equation in the Coulomb field to find an exact (in the parameter Z alpha) expression for the amplitudes of small-angle Delbruck scattering of high-energy photons. The values of these amplitudes agree with those obtained in earlier calculations, but the structure of the expressions is much simpler than that of previously known representations, which makes numerical calculations much easier. (C) 1999 American Institute of Physics. [S1063-7761(99)00807-0].