Why is there a bremsstrahlung tail?

The bremsstrahlung tail refers to the low-energy end of the photon spectrum produced during bremsstrahlung radiation, which occurs when charged particles, such as electrons, are accelerated in the electric field of nuclei. This tail arises because the radiation emitted is not limited to discrete energy levels; instead, a continuous range of photon energies is possible due to varying degrees of acceleration experienced by the electrons. As a result, some electrons can emit photons with very low energies, leading to the characteristic tail in the spectrum. This phenomenon is particularly significant in high-energy environments, such as in plasma or astrophysical contexts.