Peculiarities in the low energy range of the bremsstrahlung spectrum

Peculiarities in bremsstrahlung and polarization bremsstrahlung from fast electrons caused by the collective contribution of target's atoms to the formation of emitted photons are considered theoretically. It is shown that such collective contribution can result in the strong suppression or, in the contrary, in substantial growth of the emission yield relative to that in the case of fast electron interaction with a separate atom. Some new effects of this kind are analyzed in detail and the possibility to observe them experimentally is estimated.