Radiative correction to the equivalent-photon spectrum of a relativistic electron and the two-photon process

On the basis of the improved Weizsa\ifmmode\ddot\else\textasciidieresis\fi{}cker-Williams equivalent-photon spectrum of a fast charged particle, we calculate the radiative correction to this spectrum. The calculation involves the virtual-photon radiative correction, the soft- and hard-bremsstrahlung contributions, and the vacuum-polarization contribution. The results are used to calculate the radiative correction to two-photon production of...