SPLITTING OF A HIGH-ENERGY PHOTON IN A STRONG COULOMB FIELD

The helical splitting amplitudes of a high-energy photon in an externa l Coulomb field are found exactly with respect to Z alpha. Both screen ed and unscreened potentials are investigated. The treatment is carrie d out within the semiclassical approach, which is valid for small angl es between the momenta of all photons. A new representation is used fo r the semiclassical electronic Green's function. The resulting express ions are analyzed in detail for the case of transverse components of t he momenta of the final photons that are large compared with the elect ron mass. (C) 1997 American Institute of Physics. [S1063-7761(97)00112 -1].