NRS (Nuclear Resonance Scattering) is a way to study the hyperfinefield of solenoids.
The proces begins with the usage of synchrotron radiaton. This radiation has a broad range on the available energy, and has a constant period. Because, as the name suggests, the radiation is taken from a synchrotron which has a specific frequency.
Contrast to e.g. Mössbauerspectroscopie, the source radiation has a wide range of available energy. Therefore all excitations (or most) between hyperfinelevels of different nuclear states will take place.
These energy levels will typically all have different deëxcitation times. Moreover due to the periodically excitation via synchrotrion radiation, one will get constant deëxcitation from the different hyperfinelevels.
Each deëxcitation sequence will have its own period (couplet to the deëxcitation time). These different sequences will be measured as a superposition and will therefore create an interference patern.
This interference pattern is measured and using the shape of the pattern one can deduce hyperfine interaction parameters of the nuclei.