NONRELATIVISTIC 2-PHOTON ELECTRON BREMSSTRAHLUNG IN A COULOMB FIELD, INCLUDING RETARDATION

We study retardation effects in the two-photon electron bremsstrahlung in a Coulomb field, for the electron energy range 1-10 keV. The calcu lation is based on an exact analytic expression for the matrix element of the process, in a nonrelativistic treatment including retardation. The comparison with previous results for the Coulomb case (exact Coul omb dipole approximation or Born approximation with retardation) confi rms the importance of retardation effects in the electron energy range under investigation, as indicated before by the Born approximation.