Bremsstrahlung:Radiative Energy Loss
ìBraking radiationî:A fast electron loses energy to its environment in a nonspecific way due to Coulombic interaction with neighboring charged particles.
The static particles are much more massive than the electron, so they donít get accelerated nearly as much as the electron does: but the electron does get accelerated.
What happens when an electron is accelerated? It has to radiate! This type of Coulombically-motivated radiation is Bremsstrahlung