Mössbauer spectrometry

Nuclear gamma resonance or Mössbauer spectrometry (MS) makes use of the possibility of observing the recoilless resonant absorption of γ photons in solids. Since its discovery in 1958, the Mössbauer effect has undergone extremely rapid development, becoming a successful research method, and then a competitive instrument in the field of application and control. As with other nuclear observation techniques (nuclear magnetic resonance, perturbed angular correlations, resonant nuclear reactions...), the primary interest of the Mössbauer effect currently lies in its potential applications in condensed matter physics and chemistry; particular mention may be made of solid-state physics, magnetism, physical and applied metallurgy, coordination chemistry, catalysis, mineralogy, biology, archaeology and the fine arts.

Like other nuclear probes, Mössbauer spectrometry provides local information on the nuclei it affects, in particular their vibrational state, local electron density and effective magnetic moment. This type of data provides valuable information on the valence state of the corresponding atoms, the bonds they form with their neighbors and their position in a crystal lattice. As iron is one of the easiest nuclei to work with, metallurgy and mineralogy are prime areas for using the technique. The Mössbauer effect provides valuable data for the fundamental study of alloys and other iron compounds such as carbides and oxides. This non-destructive method is also used to test certain properties of industrial substances, such as the agglomeration state of carbon or nitrogen in steels, or the degree of oxidation of ores. Generally speaking, Mössbauer spectrometry's potential concerns the relationship between the fundamental properties of materials (electronic and magnetic structure, structural or chemical order) and their bulk average properties, which are likely to have practical applications; MS ranks among the local probe techniques.

The Mössbauer technique can only be applied to the solid state of matter, and is limited to a certain number of elements, or more precisely to certain isotopes of these elements. In the field of engineering sciences, only iron and tin are considered, due to their technological importance and their relative experimental simplicity in SM. The technique is multi-disciplinary, both experimentally and theoretically, non-destructive and suitable for in-situ analysis at high or low temperatures, but requires the use of relatively intense radioactive sources (e.g. 1 to 3 GBq).

The principle of Mössbauer spectrometry, covered in a simple manner in the first part, can be tackled without any in-depth knowledge of nuclear physics, and aims to define the physical quantities accessible by MS. The second part is devoted to the...