Semiclassical approach to the radiation theory of high energy particles in crystals and the boundary conditions problem
A method of canonical transformations for describing the radiation process of high energy particles in an external field and also in crystals using the semiclassical approximation is proposed. The main attention is paid to the problem of the boundary conditions when describing the radiation. It is shown that the radiation cross-section can be expressed through classical particle trajectories in an external field. There may be several trajectories for the same fixed boundary conditions, and the existence of this possibility leads to a specific interference picture of radiation similar to the one for the rainbow scattering of particles.