  The theory of heterodyne/stroboscopic detection of nuclear resonance
scattering is developed, starting from the total scattering matrix as a product
of the matrix of the reference sample and the sample under study. This general
approach holds for any dynamical scattering channel. The forward channel, which
is discussed in detail in the literature, reveals the speciality that
electronic scattering causes only an energy independent diminution of the
intensity. For all other channels, complex resonance line shapes in the
heterodyne/stroboscopic spectra - as a result of interference of electronic and
nuclear scattering - is encountered. The grazing incidence case is evaluated
and described in detail. Experimetal data of classical grazing incidence
reflection and their stroboscopic detection on [natFe/57Fe]10 and
antiferromagnetic [57Fe/Cr]20 multilayers are fitted simultaneously.
