Mossbauer resonant absorption cross-section

The theoretical interpretation of the effect was done by R. L. Mossbauer himself, using the theory of W. E. Lamb, Jr. (8), for neutron capture by atoms in a crystal. According to this theory the resonance-absorption cross section is given by... 

In addition to the preparation of a solid sample, one should also notice that the content of iron as well as the natural abundance of its Mossbauer isotope Fe is manifestly low. Thus, the intensity of Mossbauer resonance may have difficulty in meeting the requirement since the resonance absorption cross-section is relatively low. More often, samples containing iron have to be enriched with the isotope If the samples are purified from bacteria or cells in... 

Mossbauer spectroscopy involves the measurement of minute frequency shifts in the resonant gamma-ray absorption cross-section of a target nucleus (most commonly Fe occasionally Sn, Au, and a few others) embedded in a solid material. Because Mossbauer spectroscopy directly probes the chemical properties of the target nucleus, it is ideally suited to studies of complex materials and Fe-poor solid solutions. Mossbauer studies are commonly used to infer properties like oxidation states and coordination number at the site occupied by the target atom (Flawthome 1988). Mossbauer-based fractionation models are based on an extension of Equations (4) and (5) (Bigeleisen and Mayer 1947), which relate a to either sums of squares of vibrational frequencies or a sum of force constants. In the Polyakov (1997)... 

The Mossbauer measurements makes it possible to study a variety of interesting effects that may be brought about by the introduction of impurity in the lattice as also the modifications brought about by imperfection in the crystal lattice, since the nuclei must be bound in a crystal for this study of resonant emission (or absorption) of y-rays. Three dynamical quantities of interest, which are possible in the Mossbauer studies, are (i) Zero-phonon absorption cross-section giving the Lamb-Mossbauer factor, (ii) One-phonon absorption cross section yielding the time information as well as the information of the localized modes and through this the information on the force constant between impurity and the host atom, (iii) the second order Doppler effect yielding information about the mean square velocity of the Mossbauer probe. 

It is much more difficult to observe the Mossbauer effect with the 130 keV transition than with the 99 keV transition because of the relatively high transition energy and the low transition probability of 130 keV transition, and thus the small cross section for resonance absorption. Therefore, most of the Mossbauer work with Pt, published so far, has been performed using the 99 keV transition. Unfortunately, its line width is about five times larger than that of the 130 keV transition, and hyperfine interactions in most cases are poorly resolved. However, isomer shifts in the order of one-tenth of the line width and magnetic dipole interaction, which manifests itself only in line broadening, may be extracted reliably from Pt (99 keV) spectra. 

Maximum cross-section resonant absorption, usually some orders of magnitude, exceeds another cross-sections of interaction of y-quanta with matter. That is why the Mossbauer effect is easy observable for Fe and Sn, despite their small content in natural isotope blend ( Fe 2.2%, Sn 8.5%). Cross-section of resonant interaction reaches a maximum value for the energy E = Eq- Dependence of o on E is given by the Wigner formula... 

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