Emission Mossbauer spectroscopic

Spectroscopic techniques may provide the least ambiguous methods for verification of actual sorption mechanisms. Zeltner et al. (Chapter 8) have applied FTIR (Fourier Transform Infrared) spectroscopy and microcalorimetric titrations in a study of the adsorption of salicylic acid by goethite these techniques provide new information on the structure of organic acid complexes formed at the goethite-water interface. Ambe et al. (Chapter 19) present the results of an emission Mossbauer spectroscopic study of sorbed Co(II) and Sb(V). Although Mossbauer spectroscopy can only be used for a few chemical elements, the technique provides detailed information about the molecular bonding of sorbed species and may be used to differentiate between adsorption and surface precipitation. 

In situ emission Mossbauer spectroscopic measurement of the hyper-fine magnetic fields on trivalent Fe-57 and tetravalent Sn-119 arising from divalent Co-57 and pentavalent Sb—119, respectively, yields valuable information on the chemical structure of adsorbed metal ions at the interface between hematite and an aqueous solution. 

TABLE 17.1 Mossbauer Parameters Calculated from Emission Mossbauer Spectroscopic Data for Aqueous Suspensions of Live and Dead Cells of Azospirillumbrasilense Sp245 in the Co"-Containing Culture Medium as well as for the Cell-Free Supernatant Liquid, which were Incubated with CoCl2 for Specified Periods of Time at Ambient Temperature and then Rapidly Frozen in Liquid Nitrogen (Spectra Measured at 7= 80 lO [27,31,32]) ... 

In spite of the development of physicochemical techniques for surface analysis, spectroscopic methods applicable to the study of bonding between adsorbed metal ion species and substrate are limited, especially those applicable to in situ measurement at interfaces between solid and aqueous phases (1,2). In previous papers, we showed that emission Mossbauer measurement is useful in clarifying the chemical bonding environment of dilute metal ions adsorbed on magnetic metal oxide surfaces (3,1 ) ... 

Almost every modem spectroscopic approach can be used to study matter at high pressures. Early experiments include NMR [ ], ESR [ ] vibrational infrared [33] and Raman [ ] electronic absorption, reflection and emission [23, 24 and 25, 70] x-ray absorption [Tf] and scattering [72], Mossbauer [73] and gems analysis of products recovered from high-pressure photochemical reactions [74]. The literature contains too many studies to do justice to these fields by describing particular examples in detail, and only some general mles, appropriate to many situations, are given. 

Porphyrin is a multi-detectable molecule, that is, a number of its properties are detectable by many physical methods. Not only the most popular nuclear magnetic resonance and light absorption and emission spectroscopic methods, but also the electron spin resonance method for paramagnetic metallopor-phyrins and Mossbauer spectroscopy for iron and tin porphyrins are frequently used to estimate the electronic structure of porphyrins. By using these multi-detectable properties of the porphyrins of CPOs, a novel physical phenomenon is expected to be found. In particular, the topology of the cyclic shape is an ideal one-dimensional state of the materials used in quantum physics [ 16]. The concept of aromaticity found in fuUerenes, spherical aromaticity, will be revised using TT-conjugated CPOs [17]. 

The Mossbauer effect as a spectroscopic method probes transitions within an atom s nucleus and therefore requires a nucleus with low-lying excited states. The effect has been observed for 43 elements. For applications in bioinorganic chemistry, the 57Fe nucleus has the greatest relevance and the focus will be exclusively on this nucleus here. Mossbauer spectroscopy requires (a) the emission of y rays from... 

The Mossbauer effect involves the resonance fluorescence of nuclear gamma radiation and can be observed during recoilless emission and absorption of radiation in solids. It can be exploited as a spectroscopic method by observing chemically dependent hyperfine interactions. The recent determination of the nuclear radius term in the isomer shift equation for shows that the isomer shift becomes more positive with increasing s electron density at the nucleus. Detailed studies of the temperature dependence of the recoil-free fraction in and labeled Sn/ show that the characteristic Mossbauer temperatures Om, are different for the two atoms. These results are typical of the kind of chemical information which can be obtained from Mossbauer spectra. 

X-ray fluorescence emission (8, 9) atomic absorption (10-12), Mossbauer (13), and scanning Auger (14) spectroscopic methods and neutron activation analysis (NAA) (15-17). In addition, several exotic physical methods such as X-ray xeroradiography (18, 19) and photoacoustic analysis (20) have been applied to the study of ceramics. Of the analytical methods listed, neutron activation has been the most frequently used technique. 

In conventional Mossbauer spectroscopy, X-rays with energies corresponding to nuclear transitions (5-150keV) can be produced only by use of radioactive sources containing a parent isotope of the absorbing nucleus in an appropriate excited state from which it decays into the ground state with emission of a y-quantum. For spectroscopic applications, the y-radiation must be variable. The chemical perturbations... 

Mossbauer effect was first reported by Rudolph Mossbauer in 1958. Three years later, he won the Nobel Prize with his discovery. Since then, it is believed that nuclear y-ray emission and absorption process can take place in recoil-free fashion. In reality, of course we have both recoil and recoil-free events. Mossbauer also utilized the Doppler (velocity) shift to modulate the y-ray energy so that Mossbauer effect could be developed into a spectroscope for material characterization. The emission of y-rays with natural or nearly natural line width allows for observing in the y-ray spectra the interaction between the nucleus and its atom in solids and viscous liquids. 

Mossbauer Parameters Calculated from Emission Spectroscopic Data for Live or Dead Cells of A. brasilense (strain Sp7) Incubated with CoCb for 2 min or 1 h and then Rapidly Frozen in Liquid... 

A variety of spectroscopic techniques, however, are of value to determine the local bonding and, occasionally, oxidation states of various ions. Frequently, they can perform satisfactory quantitative analysis or estimates as well. Adsorption, emission, and Raman spectroscopy operating from the UV through the IR region of the spectrum can provide such information. These optical spectroscopies can be performed in either a transmission or surface-scattering mode based on the thickness and absorption properties of the specific sample. Nuclear magnetic resonance (NMR), Mossbauer spectroscopy, and electron spin resonance techniques are some other forms of spectroscopy frequently used to determine local bonding and oxidation states of specific species, primarily in the bulk rather than on the surface. These methods are limited to particular atoms or ions and are not universally applicable. 

The discovery of the resonant absorption of gamma-rays in lr by Rudolf Mossbauer in 1958 was a milestone in nuclear physics because it was formerly assumed that such a phenomenon could never occur due to the large recoil energies involved. The interest for this new finding was nevertheless still limited in the first years, but, a real breakthrough emerged from the fact that many isotopes showed a larger and much more sensitive effect. So, a new technique, called Mossbauer spectroscopy, was bom. The most important feature of this spectroscopic method is the extreme sharpness of the emission line which can easily be... 

Nuclear spectroscopic studies in polymer/additive research comprise nuclear magnetic resonance (NMR), nuclear quadropole resonance (NQR), electron spin resonance (ESR) and Mossbauer (absorp-tion/emission) spectroscopy (MAS, MES). When everything else has failed in elucidating difficult problems a safe, almost universally valid advice is to try magnetic resonance techniques, NMR and ESR, in this order. 

To perform the experimental measurements, several specimens containing corrosion products were taken from different parts of all of four units at Bohunice NPP. In the first step, the corrosion process in the steam generators was studied. The corrosion layers were separated by scraping the rust off the surface, and the powder samples were studied by transmission Mossbauer spectroscopy. It should be noted that the gamma spectroscopic measurements showed no evidence of the presence of low-energy y-radiation emission from the samples. Later, corrosion products were also collected from different parts of the secondary circuit components, and several filter deposits were analysed too. 

A wide variety of spectroelectrochemical methods is available and developments continue apace. Figure 1 contains a classification of methods by spectroscopic mode. Some techniques involve one or more modes of absorption, luminescence, or emission, e.g.. X-ray or Mossbauer, so a rigorous and comprehensive classification has not been attempted. Mass spectrometry... 

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