Mdssbauer effect

However, in contrast, the resonance effect increased by cooling both the source and the absorber. Mdssbauer not only observed this striking experimental effect that was not consistent with the prediction, but also presented an explanation that is based on zero-phonon processes associated with emission and absorption of y-rays in solids. Such events occur with a certain probability/, the recoil-free fraction of the nuclear transition (Sect. 2.4). Thus, the factor/is a measure of the recoilless nuclear absorption of y-radiation - the Mdssbauer effect. 

Stevens, J.G., Stevens, V.E. Mdssbauer Effect Data Index, Covering the 1975 Literature. IFI Plenum, New York (1976)... 

The ground- and excited-state magnetic moments ji are tabulated as /ig = 0.09062(3) n.m. (nuclear magnetons, /i ) and jig, = 0.1549 n.m., respectively (see Table Properties of Isotopes Relevant to Mdssbauer Spectroscopy provided by courtesy of Professor J. G. Stevens, Mdssbauer Effect Data Center, cf. CD-ROM). Considering that nuclear magnetic moments are given by the relation p, = giPj I, the nuclear g factors for Ee with /g = 1/2 and 1 = 3/2 are gg = 0.09062 X 2 and ge = 0.1549 x 2/3. With these values and taken from... 

The relevance of the Mdssbauer effect to chemistry is that now one can reinvestigate compounds such as the tin tetrahalides which were previously thought to be understood. There are molecular orbital calculations, quoted by Goldanskii, based on the assumption that the tin tetrahalides are primarily covalent in character. 

J.G. (eds.) Industrial applications of the Mdssbauer effect. Plenum Press, New York, 565-583... 

The substitution of a different metal into an enzyme provides a very useful method for studying the immediate environment of the metal site. In addition to the use of Co2 for spectral studies, appropriate substitution allows the use of physical methods such as electron paramagnetic resonance (Co . Cu2 ). the Mdssbauer effect tFe2 ). proton magnetic resonance relaxation techniques (Mir ), or X-ray crystallography (with a heavy metal atom to aid in the structure solution). ... 

In the preceding discussions, several characteristic energies were shown to be of importance for observation of the Mdssbauer effect. These necessary conditions can be expressed by the following inequalities ... 

If the above three conditions are satisfied, the Mdssbauer effect is observed, and the cross section for resonant absorption resonant absorption per unit flux of impinging y photons with energy E) is given by... 

The preceding discussions form the basis for deciding under what conditions the Mdssbauer effect will be observed. However, observation of resonance between the nuclear levels of a source and absorber is just the first step in the application of this effect to chemical and catalytic phenomena. The perturbation of the nuclear levels by the chemical environment must now be considered, since it is in the latter that information pertinent to catalysis is found. 

In the harmonic approximation of the interatomic forces, the probability of absorption without energy loss (probability of the Mdssbauer effect) in crystal can be expressed as... 

Comparing these two expressions for the Mdssbauer effect probability, one obtains the following equation ... 

Johnston, J. H. and Lewis, D. G. (1986) A study of the initially-formed hydi oly-sis species and intermediate polymers and their role in determining the product iron oxides formed in the weathering of iron. In Long, G. J. and Stevens, J. G. (eds.) Industrial application of the Mdssbauer effect.. Plenum, New York, 565-583. 

An experimental program designed to yield accurate Mdssbauer data will provide for the independent estimation of the three types of errors referred to above, to the extent that this is possible, and should lead ultimately to a realistic assessment of the accuracy and precision of the reported results. The errors commonly encountered in Mdssbauer effect experimentation will be illustrated by several examples in the following discussions. 

In this context, reliable Mdssbauer effect measurements should be reported in such a way that such comparisons can be reliably effected between different investigators and between different laboratories in... 

In the same way. the I,7Au Mfissbauer spectrum of CsAu is very similar to that of [Cs(C222) Au (Chapter 12). indicating that the Au- anion is present in both (Fig. 18.9).4J Since the Mdssbauer effect is a nuclear one. it is very sensitive to electron density at the nucleus and therefore (o both atomic charge and. character.4 ... 

Babushkina MS, Nikitina LP (1985) Mdssbauer study of cation distribution and energetics of biotite solid solution. In Applications of the Mdssbauer Effect Applications in Other Fields. YMe Kagan, ISe Lyubutin (eds) Alma-Ata, USSR 5 1683-1687... 

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