Nuclear Resonant Scattering is a spectroscopy technique that uses synchrotron radiation to do spectroscopy in the time domain instead of in the energy domain, such as in Mössbauer spectroscopy.
Synchrotron radiation is directed at a nucleus.This radiation is however not perfectly monochrome but has a certain (small) bandwidth. This bandwidth is still big enough to cover the whole range of the hyperfine splitting of the nuclear energy levels. Because of this, all the hyperfine levels in the nucleus will be excited at the same time by the incoming radiation.
After decaying back to the original levels, the intensity is measured of the radiation resulting from these decays.
The synchrotron radiation is sent to the nucleus periodically, which means that from this technique you get an intensity pattern evolving through time. This technique is effectively the Fourier transform of Mössbauer spectroscopy, making the transition from the energy domain to the time domain.
From this intensity pattern, one can get values for hyperfine parameters, such as the hyperfine field, quadrupole splitting and isomeric shift.