Electromagnetic radiation of relativistic channeling particles (the Kumakhov effect)

A new type of electromagnetic radiation characteristic for channeling in single crystals relativistic particles which has been recently predicted by Kumakhov and proved experimentally is reviewed. It is observed as one or several strong peaks in the soft part of the Bremsstrahlung, surpassing it by a factor of nearly one hundred. At moderate electron energies sharp peaks corresponding to spontaneous transitions between quantum eigenstates of the channeling particles were detected. But for high energy channeling electrons these peaks merge into one broad classical peak with the frequency determined by the collective potential of an atomic row or plane. This radiation also strongly depends on the charge sign, velocity and mass of the particle.