Mossbauer preparation

With trifluoromethanesulfonic acid, all four vinyl groups are displaced at - 78°, to give a compound that was shown by Mossbauer spectroscopy to contain both Sn(II) and Sn(IV), and that was assigned the formula Sn [Sn (S03CF3)6]. Trivinyltin carboxylates have also been prepared from the reaction between tet avinyltin and mercury(I) carboxylates, which may be generated electrochemically in situ (185). 

The preparation and characterization, and Mossbauer and epr spectra of Fe(II) and Fe(III) complexes of cyclopentadienyldithiocarboxy-late have been reported recently (261). 

In Mossbauer emission spectroscopy one prepares the catalyst with the radioactive source element (e.g. Co) and uses a suitable moving single-line absorber of Fe to record the spectra. In this way one can also study Co-containing catalysts, although strictly speaking the information concerns the iron in the catalyst that forms by the Co —> Fe decay process. 

The same Ketjen alumina described earlier was used for the Mossbauer experiments. The samples were prepared Identically, with the following exceptions. The extrudate was ground to 20-40 mesh before Impregnation, and 0.5 gram samples were prepared using 2 mCl of Co. The samples were prepared to give 8.9% Ho and 1.2%... 

Figure 8. Mossbauer spectrum of 7% w/w FePc dispersed on a high surface area carbon (XC-72). The specimen was prepared In the same fashion as described In the caption Fig. 6. The spectrum corresponds to the dry material (19).

In this chapter, we present the principles of conventional Mossbauer spectrometers with radioactive isotopes as the light source Mossbauer experiments with synchrotron radiation are discussed in Chap. 9 including technical principles. Since complete spectrometers, suitable for virtually all the common isotopes, have been commercially available for many years, we refrain from presenting technical details like electronic circuits. We are concerned here with the functional components of a spectrometer, their interaction and synchronization, the different operation modes and proper tuning of the instrument. We discuss the properties of radioactive y-sources to understand the requirements of an efficient y-counting system, and finally we deal with sample preparation and the optimization of Mossbauer absorbers. For further reading on spectrometers and their technical details, we refer to the review articles [1-3]. 

Particularly for thin Mossbauer absorbers with a low concentration of the resonance nuclide and high mass absorption, it may be problematic to apply the recommendation for sample preparation (f 0.2), because the resulting electronic absorption may be prohibitively high. In such a case, it may pay well to optimize the absorber thickness, i.e., the area density f. To this end, following the approach of Long et al. [33], we adopt the general expression ... 

Because of the complexity of sample preparation, backscatter measurement geometry (see Fig. 3.19) is the choice for an in situ planetary Mossbauer instrument [36, 47 9]. No sample preparation is required, because the instmment is simply presented to the sample for analysis. On MER, the MIMOS II SH is mounted on a robotic arm that places it in physical contact with the analysis target (e.g., rock or soil) [36, 37]. 

Most of the Zn Mossbauer experiments so far have been carried out with ZnO as absorber. De Waard and Perlow [54] used polycrystaUine ZnO enriched to 90% in Zn with various pretreatments. They intended to determine (1) the quadrupole splitting in ZnO, (2) the influence of source and absorber preparation on the width and depth of a resonance, (3) the SOD shift, and (4) the influence of pressure on the source. 

The precursor of ° Ru is ° Rh (tip, = 3 years). It is prepared by irradiating natural ruthenium metal with 20 MeV deuterons, " Ru (d, n) Rh. The target is then allowed to decay for several months to diminish the accompanying Rh activity. In a report on ° Ru Mossbauer spectroscopy [111], the authors reported on spectra of Ru metal, RuOa, and [Ru(NH3)4(HS03)2] at liquid helium temperature in standard transmission geometry using a Ge(Li) diode to detect the 127 keV y-rays. The absorber samples contained 1 g of ruthenium per cm. ... 

The source preparation for tungsten Mossbauer spectroscopy is in general cumbersome, apart from the production of a, the parent nuclide of The first... 

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