Radiation from polarized electrons in oriented crystals at high energy

Radiation from high-energy electrons in an oriented crystal can be considered in a frame of the quasiclassical operator method which appears to be a most satisfactory approach to the problem. Under some quite generic assumptions the general expression is derived for the probability of circularly polarized photon emission from the longitudinally polarized electron in oriented crystal. The particular mechanism of radiation depends on interrelation between the angle of incidence ϑ0 (angle between the momentum of initial electron and axis (plane) of crystal) and angle ϑv ≡ V0/m (V0 is the scale of a potential of axis or a plane relative to which the angle ϑ0 is defined). When ϑ0 ≪ ϑv one has magnetic bremsstrahlung type of radiation (with corrections ∝ϑ02 which are due to inhomogeneous character of field in crystal). When ϑ0 ≫ ϑv one obtains the theory of coherent bremsstrahlung, while for ϑ0 ⩾ ϑv one arrives to the modified theory of coherent bremsstrahlung. At high-energy radiation in oriented crystals is strongly enhanced comparing with standard bremsstrahlung.