Mdssbauer isomer shift

Wagner, F.E., Wagner, U. Mdssbauer Isomer Shifts, North Holland, Amsterdam (1978), p. 431... 

Reasonable results have also been obtained for Zn Mdssbauer isomer shifts in zinc chalcogenides from LMTO band calculations (Svane and Antoncik, 1986) and for Sb compounds (Ravenak et al., 1983) using the DYM-Aot method. The overall conclusion must be that the time is ripe for the systematic calculation of Fe isomer shift and electric-field-gradient values in Fe-0, Fe-S, and other polyhedra using ab initio Hartree-Fock-Roothaan or DVM-Aa methods. 

Nieuwpoort, W. C., D. Post, and P. Th. van Duijnen (1978). Calibration constant for Fe Mdssbauer isomer shifts derived from ab initio self-consistent-field calculations on octahedral FeFj, and Fe(CN)s clusters. Phys. Rev. B17, 91-98. 

Mdssbauer isomer shifts, and data from visible, infrared, and ESR spectroscopy. Mo NMR chemical shifts have also been... 

Studies on concentrated lanthanide metallic systems have also made it possible to establish a correlation between nonintegral valence (observable in concentrated lanthanide systems through lattice constant, Mdssbauer isomer shift, soft X-ray absorption and X-ray photoemission spectroscopy measurements) and nonmagnetic behavior of a lanthanide ion below the characteristic temperature. This has led to the concept of valence fluctuations (or interconfiguration fluctuations) which has stimulated the current intense activity among theorists and experimentalists alike. 

Similar to the isomer shifts in Mdssbauer spectroscopy, the results from photo-electron spectroscopy are sensitive to the local chemical environment of an atom. [88] However, whereas Mdssbauer spectroscopy reflects the initial electronic structure of the system under investigation, probes the state after elimination of an electron. [84] Furthermore, whereas the Mdssbauer isomer shift gives informations on the s electron density within the nuclear volume, XPS results describe the overall electronic charge denaty of an atom. As such, Moss-bauer spectroscopy and XPS compliment each other in an ideal manner. 

Mdssbauer Isomer Shifts, eds G.K. Shenoy and F.E. Wagner (North-Holland, Amsterdam) p. 15. 

Efforts were made to obtain spectroscopic evidences for intermediates. The binding of ACV to iron(II) has been indicated by the decrease of the Mdssbauer isomer shift of the iron(II) center from 1.3 to 1.1 mm/s upon addition of ACV [156]. The appearance of a band at 508 nm after addition of ACV to an IPNS/NO complex also supports the binding of ACV to iron(II) [156, 157]. The similar electronic spectral change was observed with copper model complexes [162]. Support for the Fe-S bond in the ternary complex was obtained by EXAFS analyses [164, 165, 182]. EPR studies indicate the water coordination to the ferrous ion in an IPNS/ACV/NO complex as a model for a ternary species [156]. 

Fig. 7.57 Plot of the isomer shift 5 of the 36.2 keV Mdssbauer transition of Os versus Dirac-Fock values for the electron density differences at the Os nuclei in free ion 5d configurations. The numbers of the data points refer to the numbering of the compounds in Table 7.9 (from [258])...

Table 7.12 Isomer shift 5 (with respect to the source of Au in Pt metal at 4.2 K), line width F, and percentage resonance effect / from Pt (99 keV) Mdssbauer measurements on platinum compounds at 4.2 K by Riiegg and coworkers [329, 332, 333]...

The Mdssbauer spectrometer was equipped with a 10 mC 5 Co/Rh source maintained at room temperature, A Northern NS-yOO multichannel analyser was used for taking the spectra. The Mdssbauer parameters were determined by least square computer programme. Tht isomer shift (5) was calculated with reference to a-Fe. The diaracieristics of iron in various iron molybdates and iron antimonate arc given in table I. 

Table 10. Comparison of Quadrupole Splittings (AEQ) and Isomer Shifts (S) for some Xe(II) and Xe(IV) Compounds, derived from 129Xe Mdssbauer Spectra (Ref.40 )...

Sn Mdssbauer data have been reported for 3-Sn-l,2-B9C2H, 8 = 4.67 0.04mm s, AE0 = 3.83 0.004 mm s. The isomer shift is consistent with a formal Sn" oxidation state, while the large quadrupole splitting arises from the marked asymmetry of the molecular structure.76... 

Fig. 10. Mdssbauer spectra of reduced (left panels) and oxidized (right panels) PS-I core complex at 80 K (top panels) and 4.2 K (bottom panels), The lower spectrum in each of the left panels was corrected for the unreduced component. The table at top right lists the experimentally determined isomer-shift (IS) and quadrupole-splitting (QS) parameters for oxidized and reduced core complexes at 77 K lower table lists isomer-shift values reported in the literature for other [4Fe 4S] and [2Fe 2S] clusters. Data source Petrouleas, Brand, Parrett and Golbeck (1989) A Mossbauer analysis of the low-potential iron-sulfur center in photosystem I Spectroscopic evidence that Fx is a [4Fe-4S] cluster. Biochemistry 28 8982.

The thermal shift 6j of the Mdssbauer spectrum is the sum of a contribution due to the second-order Doppler effect (6sod) and a possible contribution due to an intrinsic dependence of the isomer shift (8j) on temperature. The second-order Doppler shift is proportional to the mean square velocity of the Mdssbauer nucleus. For the purpose of a comparison with thermodynamic data, the SOD shift may be described in terms of the Debye approximation,6... 

The inadequacy of the Debye approximation in describing the details of the frequency distribution function in a real solid is well known. This results in noticeable disparities between Debye temperatures derived from the results of different experimental techniques used to elucidate this parameter on the same solid, or over different temperature ranges. Substantial discrepancies may be expected in solids containing two (or more) different atoms in the unit cell. This has been demonstrated by the Debye-Waller factors recorded for the two different Mdssbauer nuclei in the case of Snl4,7 or when the Debye-Waller factor has been compared with the thermal shift results for the same Mdssbauer nucleus in the iron cyanides.8 The possible contribution due to an intrinsic thermal change of the isomer shift may be obscured by an improper assignment of an effective Debye temperature. 

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