Experimental methods in chemical engineering: Mössbauer spectroscopy

When a free nucleus absorbs or emits a gamma ray, it recoils to conserve energy, just like a gun recoils after shooting a bullet. Nuclei bound to a crystal lattice conserve energy when they absorb or emit gamma rays from a nuclear transition as they are fixed so their movement is restricted. This restriction is recoilless nuclear resonance fluorescence — the Mössbauer effect. The energy transmitted through a sample reveals its electronic and molecular structure and magnetic properties but only when the atoms in the source and sample are the same isotope — 57 Co/ 57 Fe is the most common couple. So, many of its applications are to identify iron species or how they change as a function of environmental conditions, like corrosion. A bibliometric map identified six major clusters centred around: nanoparticles and magnetite (Fe 3 O 4 ), crystal structure and spectroscopy, oxidation and catalysis, X-ray diffraction (XRD) and Raman spectroscopy, 57 Fe and cathodes, and Co and thin films. In the last 30 years, the number of articles per year that mention the technique has hov-ered around 1250. More recently, Mössbauer spectroscopy has experienced a great rediscovery, particularly in the industrial sector for the solution of some problems, but also in space exploration.