Comment on the use of the low-energy theorem in determining the bremsstrahlung spectrum

Much understanding of the bremsstrahlung spectrum can be obtained from the behavior at its two end points. The low-energy theorem can be used to obtain the soft-photon end point from elastic scattering; this may be combined with data from the hard-photon portion of the spectrum to interpolate through the soft-photon region, which is difficult to calculate directly because partial-wave series converge slowly. The low-energy theorem may also be used to show that, contrary to statements in the literature, the ratio of the Born approximation to the exact cross section approaches unity at the soft-photon end point for the Coulomb potential but not for a screened potential.