Nuclear Diffraction of Synchrotron Radiation in Laue Geometry: Quantum Beat Shift

Time spectra of nuclear resonant diffraction of synchrotron radiation in nearly perfect single crystals of $^{57}FeBO_3$ and $^{57}Fe_3BO_6$ have been measured in Laue geometry. Characteristic shifts of the quantum beat pattern proportional to the crystal thickness were observed. This shifts originate from the thickness dependence of the relative phases of the interfering hyperfine components of the scattered radiation. The phase velocities of the components are different because of a complicated dispersion law where all 14.4 keV nuclear hyperfine transitions of $^{57}$Fe contribute to the scattering amplitudes. A kind of interferometry employing beam splitting in energy was demonstrated in the experiment