Nuclear resonant scattering (NRS)

This method uses a combination of the brilliant intensity of third generation synchrotron sources and the excellent characteristics of Quasielastic Mössbauer Spectroscopy. The resonant effect with synchrotron radiation was observed for the first time 1985 by Gerdau et.al. [12]. NRS measurements contain information about the hyperfine parameters of atoms. In [13] it was demonstrated that this technique is capable to measure diffusion coefficients. Based on the theory of Smirnov and Kohn [8] the results of QMS measurements on Fe$_{3}$Si have been verified. A series of measurements in different geometries (transmission [14,15], Bragg reflection [16] followed. All these experiments provide information about the bulk diffusion. Introducing the depth selectivity of the grazing incidence geometry into an NRS experiment and especially the element and isotopic sensitivity one moves the borders for the application of nuclear resonant experiments to the field of metallic thin films and multilayers.
The principle idea of an NRS experiment is to measure a time response of a sample enriched with Mössbauer isotopes: The synchrotron radiation is used to excite the resonant nuclei in the sample into a high energy state. One part of the synchrotron radiation is scattered by the electrons (ps process). This part defines the starting point of the measurement. A small part is absorbed and re-emitted by the resonant nuclei with a characteristic lifetime (141 ns for the 14.4 keV $^{57}$Fe). The re-emitted intensity (delayed intensity) I(t,k$_{R}$) is collected as a function of time $t$ and orientation $k_{R}$ of the sample. More details about the experimental setup can be found in section .