Angular distribution of photons emitted in collision of low-energy electrons with noble gases

The angular distribution of photons emitted at interaction of low-energy electrons with atoms of noble gases is investigated. The angular asymmetry of the bremsstrahlung cross section is significant and strongly depends on the electron and photon energies. The effect of polarization radiation is considered. It is shown that this effect is noticeable even below the electroluminescence threshold, in contrast to the generally accepted point of view. In the case of argon, the account for the polarization radiation improves the agreement between the predictions and the available experimental data for the yield of bremsstrahlung photons.