Resonant scattering is a form of scattering in which the incoming scattering frequency
remains the same after the scatter proces. This means that a particle in a certain
energy state will absorb the photon and emit it with the same energy. Nuclear
resonant scattering means that this proces is done with nuclei. Due to the natural
linewidth of the energy levels and various other broadening evenent, this is
quite hard to achieve. Since synchrotron radiation exists in the range from
infra-red to x-rays, it can be used to measure lots of propreties of materials.
One of the main investigation field is the spin structure of materials in surface
layers, but also deeper layers. This because the transitions are depending on a change
in spin of the nucleus, with other words a change in nuclear magnetic moment.