ON THE LINE SHAPE OF BACKWARD EMITTED PARAMETRIC X-RADIATION

摘要

Parametric X radiation, emitted in opposite direction of an electron which traverses a semi infinite single crystal on a hypothetical straight trajectory, features a Lorentzian line shape with extremely narrow width. However, small angle scattering of the electron in the Coulomb potential of the crystal atoms results in a stochastic change of the electron direction. The latter leads to a line broadening which can be understood essentially as a stochastic frequency modulation of the exponentially damped wave train. The line shape has been calculated analytically by well known probabilistic methods. Results are quoted for various reflections of a silicon single crystal at an electron beam energy of 855 MeV.