Exact point-Coulomb calculations of differential cross sections of atomic-field bremsstrahlung

Angular bremsstrahlung cross sections are computed with a point-Coulomb potential. In this calculation, the Dirac equation is expanded in partial waves, the radial functions are the classical ones, and the amplitude is given in an analytical form. We give some curves for the energy range 50 keV-2.5 MeV and for the case $\frac{k}{T}\ge 0.8$, where screening effects are small ($T$ is the kinetic energy of the incident electron, and $k$ refers to the emitted photon). In particular, we consider the tip region of the bremsstrahlung spectrum at 1.84 MeV according to the experiment of Starek, Aiginger, and Unfried. The discrepancy between experimental and theoretical results is very large for low $Z$.