Klein-Gordon Formulation of X-ray Diffraction in the Laue Cas

The Takagi-Taupin equations, the fundamental equations for X-ray diffraction deduced from the Maxwell equations, are considered. The connection between the Takagi-Taupin equations and the Klein-Gordon equation is shown. A method of solution of these equations using external differential form formalism is proposed. The solutions for both a narrow and a wide incident beams as a function of boundary conditions is analyzed. The so-called spherical and quasi-plane waves used in the X-ray experimental methods are derived from.