On the Question of Interference in Radiation Produced by Relativistic   Channeled Particles
  Two approaches used in the description of the channeling radiation emitted from relativistic positrons are compared with each other.   In the first (traditional) case, the probability of the process is proportional to a sum of absolute squares of the amplitudes of the transition between two states with definite transverse energy levels of the positrons traversing single crystals. In the second case, we begin with calculation of the sum of amplitudes for transition between states with different transverse energy levels for corresponding radiation frequency, and then the sum is squared. One must keep in mind that the latter approach can be used only in the case when positrons move in a nearly harmonic planar potential with equidistant transverse energy levels. It is shown that the calculation based on the second approach can give rise to a peak structure in the spectrum when the number of transverse energy levels is much greater than one. 
V.F.Boldyshev and M.G.Shatnev (National Science Center Kharkov   Institute of Physics and Technology)