Mössbauer Effect -- from Eric Weisstein's World of Physics

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Mössbauer Effect

In the emission of -ray photons from an atom corresponding to a transition to nuclear ground state, momentum must be conserved, so the atom must have a small recoil. Energy balance then implies gamma rays are emitted with a spread of energies. When an atom is part of a crystal lattice, however, the entire lattice may recoil resulting in a quantized vibrational energy termed a phonon. If no phonon is emitted or absorbed, the emitted gamma rays have a very small spread of energies, given by

This is the Mössbauer effect. It is often used in Mössbauer spectroscopy.

Mössbauer was the first to observe this effect in 1958. He used gamma rays of energy 0.129 MeV, corresponding to the transition from ground to the first excited state of . He was awarded the Nobel Prize in 1961. The Mössbauer effect has also been used to verify the prediction of gravitational redshift (the frequency of electromagnetic radiation is dependent on the strength of the gravitational field). Pound Eric Weisstein's World of Biography and Rebka Eric Weisstein's World of Biography first carried out such experiments in 1959 (Pound and Rebka 1959).

Gravitational Radiation, Phonon

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