Coherent forward-scattering amplitude in transmission and grazing incidence Mossbauer spectroscopy

The theory of both transmission and grazing incidence Mossbauer spectroscopy is reanalyzed. Starting with the nuclear susceptibility tensor a common concise first-order perturbation formulation is given by introducing the forward-scattering amplitude into an anisotropic optical scheme. Formulas of Blume and Kistner as well as those of Andreeva are rederived for the forward-scattering and grazing incidence geometries, respectively. Limitations of several previously intuitively introduced approximations are pointed out. The grazing incidence integral propagation matrices are written in a form built up from 2 x 2 matrix exponentials which is particularly suitable for numerical calculations and practical fitting of both energy domain (conventional source experiment) and time domain (synchrotron radiation experiment) Mossbauer spectra.