Impurity Mossbauer spectroscopy

A substantial advantage of emission Mossbauer spectroscopy in comparison with the transmission technique is that if the material to be investigated contains heavy elements, then the required dopant concentration (e.g., Co) may be 1-2 orders of magnitude lower in the emission experiment than the Fe concentration in an analogous transmission experiment. This is in connection with the intensity loss of the Mossbauer radiation due to electronic absorption, which is always self absorption in the source and regular absorption in the absorber (Vertes and Homonnay 1997). Low dopant concentration is very important in impurity Mossbauer spectroscopy, where the investigated material does not contain a Mbssbauer element thus, a conveniently measurable Mbssbauer nuclide is introduced artificially as an impurity with a potential risk of perturbing the physicochemical properties of the host phase. 

MS2 NiSAl-91 < X < 2.1) Nii j,CUySi.93 (0.03 < y < 0.1) Investigation of structural, electronic, and magnetic properties by means of X-ray diffraction, densitometry, resistivity, susceptibility, and Ni Mossbauer spectroscopy as function of x temperature of phase transition from semimetalhc to metallic state as function of x different Ni sites with different (l/f l) and different angle between H and EFG axis effect of Cu impurities... 

An iron-promoted cobalt molybdate catalyst (Fe0 03Co0.9 7MoO4) was studied by Maksimov et al. [195,196] with respect to the role of iron in the transfer of charge. Iron strongly enhances the catalytic activity and at the same time increases the conductivity by a factor of 100. Mossbauer spectroscopy reveals that 4% of the iron ions are present as Fe2+ impurity . This fraction is doubled at steady state reaction conditions, and indicates participation of iron in the charge transfer process. 

Accurate and reproducible Mossbauer spectra of supported iron catalysts require the prevention of the adsorption of impurities including oxygen and water onto the highly reactive sample surface. Cells designed to allow chemical reactions and in vacuo pretreatments at temperatures up to 673 K while the Mossbauer spectrum is being recorded have recently been reported and represent a significant and important development in the application of Mossbauer spectroscopy to catalytic and surface studies (109-111). 

Sample purity is a key concern. The NRVS experiment is a bulk technique sampling all Fe nuclei, and impurities that also contain the probe nucleus may confound quantitative data interpretation. Impurities may be introduced during sample preparation or may result from sample instability during measurement. Because of this, care must be taken to ensure purity and reproducibility as Judged by Mossbauer see Mossbauer Spectroscopy), singlecrystal X-ray diffraction, electronic absorption spectroscopy (see Electronic Spectroscopy), Raman spectroscopy or other qualitative techniques. 

The original report of the preparation of [Fe"Cp2l°[TCNE]° described that it exhibited ferromagnetic behavior. A subsequent reinvestigation revealed the presence of Fe(lll) via Fe Mossbauer spectroscopy, and that decomposition induced from the grinding synthesis undoubtedly was the source of the magnetic impurity. " ... 

It is evident that Mossbauer spectroscopy can be a handy tool in differentiating between various coal fields on the basis of the Fe mineral composition of the coal. It should, however, be noted that a detailed analysis of all coal seams needs to be done to determine the run-of-mine coal iron mineral composition. The technique is also suitable for determining the iron components and the presence of sulfur associated with the iron-bearing minerals as part of the impurities found in coal. 

Mossbauer spectroscopy has also found considerable applications in the investigation of mineral systems. Much of this work has involved the determination of the number and structure of the chemical phases within certain minerals and has been of both scientific and technological importance. The importance of small amounts of doping and impurities in affecting the Mossbauer spectrum provides a significant feature of much of this work. 

The answer was found by Mossbauer spectroscopy. The parameters from the I spectrum are given in Table 6.4 [17]. In the spectrum of there was one set of lines, but in that for l2Br2Cl4 there were two sets of lines. From this, we can conclude that there are non-equivalent iodine atoms. Since the sets were of equal intensity, it was most unlikely that one set was due to an impurity, and so both sets were assigned to l2Cl4Br2. 

The probe atoms can be one of the constituents of the material, or they can be impurities introduced into the material from the outside by melting, by diffusion, or by implantation. The former processes make use of the thermal motion of the atoms, while the implantation process injects energetic probe atoms using an accelerator. In this tutorial we will further discuss implantation Mossbauer Spectroscopy , i.e., the probe atoms will be first implanted into a material, and subsequently Mossbauer spectra will be measured by detecting emitted y-rays and electrons. The spectra will provide us with atomistic information on the probe atoms through the hyperfine interactions. This situation may be well compared with an analogy of a spy which is sent to a place to gather information, and he/she will... 

As stated before, iron impurities in Si have been intensively investigated for more than 50 years by different experimental techniques [44] including Fe Mossbauer spectroscopy. This is because Fe impurities can be easily incorporated into Si... 

We hope to have demonstrated the enormous resolving power on atomistic scale of emission Mossbauer spectroscopy for such smdies. For Fe impurities in Si, with their extremely complex behavior, these techniques have clearly shown their merits and have substantially contributed to our understanding of the behavior of Fe impurities in Si. 

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