Method of approximate treatment of the relativistic compound free-free matrix elements

We extend the method introduced recently by Korol for the approximate calcu lation of the compound relativistic free-free matrix elements. The method i s based on the accurate treatment of the diagonal singularities in the one- photon relativistic matrix elements, which appear in the compound matrix el ement. For the case of relativistic projectile scattering in the field of a short- range potential we present the evaluation of the singular parts of the free -free single-photon matrix elements. The result is used to treat approximat ely the amplitude of the two-photon bremsstrahlung (2BrS) process for the r elativistic electron. This is done for the first time.