The Mossbauer effect is the recoil-free emission of gamma radiation from a solid radioactive material. Since the gamma emission is recoil-free, it can be resonantly absorbed by stationary atoms, i.e., also in a solid. The nuclear transitions are very sensitive to the local environment of the atom and Mossbauer spectroscopy is a sensitive probe of the different environments an atom occupies in a solid material.
Production of gamma rays for 57Fe Mossbauer spectroscopy
Approximately 90% of the 57Fe nuclear excited state decays through the intermediate level to produce 14.4 keV gamma radiation. These gamma photons can then be absorbed by 57Fe in a sample.
The gamma ray source is a radioactive element that is mechanically vibrated back and forth to Doppler shift the energy of the emitted gamma radiation. The schematic below shows a transmission Mossbauer experiment. As the energy of the gamma radiation is scanned by Doppler shifting, the detector records the frequencies of gamma radiation that are absorbed by the sample.
Schematic of an experimental set-up for transmission Mossbauer spectroscopy
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Copyright © 1996 by Brian M. Tissue