NRS or nuclear resonant scattering is a technique used to study hyperfine transitions. It uses photons generated from a synchrotron to excite the nuclear states.
As the photons that are produced from the synchrotron have a wide variety of energies, a lot of the excited states can be obtained at the same time.
These excited states have different lifetimes, the photons emitted by de-excitation are then captured by a detector. These de-excitation periods are unique to the transition but all the de-excitations are measured at the same time, which means it will form an interference pattern. From this interference pattern it is possible to study the characteristics of the nucleus.