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Mössbauer Spectroscopy as a Tool for Materials Research
Published online by Cambridge University Press: 29 November 2013
Extract
In 1958 Rudolph L. Mössbauer reported his discovery of a simple, practical way of observing nuclear gamma ray resonance. One of the remarkable features of the discovery was the high precision with which energy changes can be measured: energy resolutions of one part to 1011 −1013 are possible. With this high resolution capability it is possible to measure hyperfine interactions between the nucleus of an atom and its electronic environment. These interactions affect the line shape which can be described by several experimental Mössbauer parameters. The three primary parameters are the isomer shift (δ), the quadrupole splitting (Δ), and the magnetic hyperfine interaction.
The isomer shift, determined by the position of the centroid of a set of lines in a spectrum, is proportional to the electron density at the nucleus. Since only s electrons have a probability of being at the nucleus, it is possible to obtain electronic structure information such as oxidation state and population of certain molecular orbitals.
The quadrupole splitting results when the electron environment surrounding the Mössbauer nucleus is not spherical in its charge distribution. Specifically, Δ is proportional to the imbalance in electron density between the axial and equatorial directions. When this hyperfine interaction is present, there is a quadrupole splitting; i.e., a single spectra line will split into two or more lines.
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- Copyright © Materials Research Society 1986
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