Mössbauer effect

It involves the resonant and recoil-free emission and absorption of gamma radiation by atomic nuclei bound in a solid.

In the Mössbauer effect, a narrow resonance for nuclear gamma emission and absorption results from the momentum of recoil being delivered to a surrounding crystal lattice rather than to the emitting or absorbing nucleus alone.

Mössbauer proposed that, for the case of atoms bound into a solid, a fraction of the nuclear events could occur essentially without recoil under certain circumstances.

[1][2] The discovery was rewarded with the Nobel Prize in Physics in 1961, together with Robert Hofstadter's research of electron scattering in atomic nuclei.

[3] In the case of a gas, the emitting and absorbing bodies are atoms, so the mass is relatively small, resulting in a large recoil energy, which prevents resonance.

In fact, gamma rays can be used as a probe to observe the effects of interactions between a nucleus and its electrons and those of its neighbors.

Zero-phonon optical transitions, a process closely analogous to the Mössbauer effect, can be observed in lattice-bound chromophores at low temperatures.