Conversion Electron Mossbauer Spectroscopy

Abstract

Although most ⁵⁷Fe Mössbauer spectra are obtained with transmission geometry, several reflection (backscattering) techniques have been recently published. The scattering technique eliminates the need of sample preparation and provides a method for nondestructive testing of surfaces. The initial scattering experiments made use of the re-emitted 14,4 keV gamma radiation. However, due to the internal conversion process, this method is only 10% efficient, and the radiation is converted into 6.3 keV X-rays and conversion electrons. The atomic absorption of the gamma and X-ray radiation limits the penetration depth to 0.0005 inches. The 7.3 and 5.5 keV conversion electrons have a very limited range, less than 3000 Å in iron. The detection of X-rays thus primarily provides a bulk sample analysis, while the conversion electrons provide information on thin surface films (50 to 3000 Å), with applications in surface corrosion, surface absorption, catalysis, surface stresses, etc.