On the applications of Mossbauer Spectroscopy to the study of surfaces

Mossbauer Spectroscopy is a very useful and well-known technique for the study of mainly Fe-containing materials. Most of the measurements with this spectroscopy are performed in the transmission mode, while for the study of surfaces the back-scattering mode is the preferred option. Backscattered radiation contains "resonant" and "non-resonant" radiations, the first originated as a consequence of the relaxation process, which follows resonant absorption (Mossbauer Effect), being the signal, and the second being due to the photoelectric and Compton interactions, the noise. The relaxation process is rather complex and involves both nuclear and atomic relaxations, producing conversion and Auger electrons, and gamma and X-ray photons, all of them of well defined energies, whose probability to leave the surface is related to their nature, energy and track within the solid. The detection of any of these emitted radiations provides a valuable tool to obtain spectra with varying depth resolution.