Radiation emitted by electrons of matter interacting with ultrarelativistic charged particle

The recoil bremsstrahlung of a group of electrons of an atom molecule interacting with an uniformly and linearly moving ultrarelativistic particle is studied. The cross sections of radiation of individual recoil electrons in bremsstrahlung are shown not only to be added up, but there occurs interference of the radiations. The angular distribution of radiation of atom recoil electrons is sharply nonisotropic for (ωr/c)>>1 and is concentrated mainly in a small cone along the motion of a charge, that is notable for the X-ray transition radiation, produced by an ultrarelativistic particle on marcoscopic objects. A comparison is made of the cross sections of bremsstrahlung and transition radiation