Increase of parametric X-ray intensity due to the Borrmann effect

Parametric X-ray radiation (PXR) from relativistic electrons in a crystal with a thickness larger than the X-ray absorption length is considered. The characteristics of this radiation are analysed in detail taking into account the dynamical diffraction theory. It is shown that the PXR intensity increases and its dependence on the electron energy changes when the X-ray quanta are emitted under conditions of anomalous absorption (the Borrmann effect). The details of the PXR angular distribution and its comparison with the experimental data are also discussed.