Conversion electron Mössbauer spectroscopy and the study of surface properties and reactions

Unlike transmission Mössbauer spectroscopy which, in order to be of widespread utility in surface science, requires high-area solids, conversion electron Mössbauer spectroscopy (CEMS) is applicable to a wide range of low-area materials containing iron (or tin). The necessary conditions required for optimal detection of internally converted electrons (which are emitted from distances of ca. 300 nm below the exterior surface) are outlined, and the surface sensitivity of the technique demonstrated by reference to, inter alia, the determination of the rate coefficient of the parabolic oxidation rate of iron at 500°C and the detection of goethite as a weathering product of the mineral siderite. The application of this technique to other problems in materials science is discussed, and factors governing the characteristics of depth-profiling of specimens of oxidized or corroded iron (or iron-containing material) are discussed by reference to an energy analyzing spectrometer, the essential features of which are described. The merit of acquiring depth sensitive CEM spectra is illustrated by reference to the detection of a doublet which is associated with the iron/oxide interface. © 1978.