Surface and interface investigations by nuclear resonant scattering with standing waves

The main features of the reflectivity spectroscopy ("coherent spectroscopy") in energy, time and angular scales are considered. They are the enhancement or suppression of different hyperfine contributions to the spectra, strong dependence of these effects from the order of the Bragg reflectivity and from the slight angular shifts in the vicinity of the Bragg maximum, phase shifts of the quantum beats in the time spectra, shift of the angular position of the delayed reflectivity maximum relative prompt Bragg peak. These effects are caused by the depth distribution of the resonant nuclei, standing wave creation in the reflecting multilayers or thin films and also by the unhomogeneity along the surface of the resonant nuclei with different hyperfine parameters. The simple explanation is presented on the bases of the kinematical approach of the reflectivity theory. Experimental are discussed on the bases of the kinematical approach of the reflectivity theory.