Mdssbauer effect spectroscopy

R atoms. This follows from the isomer shift results obtained by means of Eu, Dy and Gd Mdssbauer effect spectroscopy, which indicate that the R atoms donate electrons to the H atoms. These findings are in agreement with the fact that there is virtually no difference in electronegativity between H and the 3d metals but a considerable electronegativity difference between R and H. 

Dunlap, B.D. Mdssbauer effect data index. In Stevens, J.G., Stevens, V.E. (eds.) An Introduction to Electric Quadrupole Interactions in Mdssbauer Spectroscopy. Adam Hilger, London (1972)... 

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... 

Fig. 5.4 In order to cover all possible transitions in the absorbing nucleus, the energy of the source radiation is modulated by using the Doppler effect. For 57Fe the required velocities fall in the range between — 1 and +1 cm s-1. In Mdssbauer emission spectroscopy, the sample under investigation is the source, and a single line absorber is used to scan the emission spectrum.

The Mdssbauer effect on the Fe nuclei in biotite.] Kristallografiya 17 328-331 PopperP (1951) Transmission of natural and synthetic mica in the ultra-violet. Nature 168 1119-1120 Raclavasky K, Sitek J, Lipka J (1975) Mdssbauer spectroscopy of iron in clay minerals. 5th IntT Conf Mdssbauer Spectroscopy, Proc Part II, p 368-371... 

L.H. Bowen, E. De Grave, R.E. Vandenberghe, Mdssbauer effect studies of magnetic soils and sediments, in Mdssbauer Spectroscopy Applied to Magnetism and Material Science, vol. 1, ed. by G.J. Long, F. Grandjean (Plenum, New York, 1993), pp. 115-159... 

The Mdssbauer effect should in principle provide useful information with respect to the bonding in rare earth complexes (Ofer et al., 1968) since the isomer shift is dependent on the electron density at the nucleus. A large number of rare earth nuclei are suitable for Mdssbauer spectroscopy, but only for Eu have complexes been extensively studied. Although a number of early papers appeared, the results were based on the report that the isomer shift in EujO relative to EuFj was less than 0.05 mm s whereas recent investigations have shown that for commercial EU2O3 the Eu isomer shift relative to EuFj-2H20 is... 

The previous chapters are exclusively devoted to the measurements and interpretation of Fe spectra of various iron-containing systems. Iron is, by far, the most extensively explored element in the field of chemistry compared with all other Mdssbauer-active elements because the Mossbauer effect of Fe is very easy to observe and the spectra are, in general, well resolved and they reflect important information about bonding and structural properties. Besides iron, there are a good number of other transition metals suitable for Mossbauer spectroscopy which is, however, less extensively studied because of technical and/or spectral resolution problems. In recent years, many of these difficulties have been overcome, and we shall see in the following sections a good deal of successful Mossbauer spectroscopy that has been performed on compounds of... 

Fig. 2.44. Mossbauer spectroscopy (a) nuclear transitions giving rise to the Mossbauer effect in Fe (b) principles involved in the Mossbauer spectrometer (c) Mdssbauer resonant absorption of iron in different crystal environments and the resulting spectral types. (After Vaughan and Craig, 1978 reproduced with the publisher s permission).

The two metal nuclei that can be studied by Mdssbauer spectroscopy and are relevant to metallocenes are Fe and " Sn. Spectra from both nuclei have been used to examine the electronic effects of substitution on metallocenes. 

The conclusion that the cobalt and iron complexes 2.182 and 2.183 are formally TT-radical species is supported by a wealth of spectroscopic evidence. For instance, the H NMR spectrum of the cobalt complex 2.182 indicated the presence of a paramagnetic system with resonances that are consistent with the proposed cobalt(III) formulation (as opposed to a low-spin, paramagnetic cobalt(IV) corrole). Further, the UV-vis absorption spectrum recorded for complex 2.182 was found to be remarkably similar to those of porphyrin 7r-radicals. In the case of the iron complex 2.183, Mdssbauer spectroscopy was used to confirm the assignment of the complex as having a formally tetravalent metal and a vr-radical carbon skeleton. Here, measurements at 120 K revealed that the formal removal of one electron from the neutral species 2.177 had very little effect on the Mdssbauer spectrum. This was interpreted as an indication that oxidation had occurred at the corrole ligand, and not at the metal center. Had metal oxidation occurred, more dramatic differences in the Mdssbauer spectrum would have been observed. 

The static and dynamic Janh-Teller effects in copper(II) [Cu(diAMHsar)](N03)4 H20 sarcophaginate and the dynamic one in analogous iron(II) complex were detected by variable temperature EPR, optical, and magnetic studies, and by Fe Mdssbauer spectroscopy, respectively [245, 246], and calculated using a density functional approach [247]. 

As in all other spectroscopic techniques, the numerical data extracted from the experiment can only be related to the solution of structural problems via results that have been cataloged for reference or model substances whose spectra are well understood in terms of their structural implications. To effect such comparisons in Mdssbauer spectroscopy, the... 

The Mossbauer effect is the emission and resonant absorption of nuclear y-rays studied under conditions such that the nuclei have negligible recoil velocities when y-rays are emitted or absorbed. This is only achieved by working with solid samples in which the nuclei are held rigidly in a crystal lattice. The energy, and thus the frequency of the y-radiation involved, corresponds to the transition between the ground state and the short-lived excited state of the nuclide concerned. Table 2.4 lists properties of several nuclei which can be observed using Mdssbauer spectroscopy. 

The greater part of the data included in this book was published before the change to the use of the SI system of units began to take effect. In practice this has had little effect on Mdssbauer spectroscopy, and we have tended to use the originally quoted figures, giving conversions where appropriate. The following notes may be of assistance ... 

Mossbauer Spectroscopy. Mdssbauer spectroscopy has been used as a powerful technique to probe the electronic structure of the five- and six-coordinate ferrous nitrosyl porphyrins. The isomer shifts of both types of complexes (5 0.35 mm s ) are similar and show temperature dependences that are consistent with a second-order Doppler effect, but are slightly smaller than those of most other iron(II) porphyrin complexes (5 0.45 mm Unlike the isomer... 

Anomalous structures (e.g. bcc gold, fee lithium) have sometimes been found these seem to occur most frequently with metals of low sublimation enthalpy, and less often with palladium and platinum. Their formation may be linked to an epitaxial effect of the support on which they are formed and grow. Clearly developed crystal planes were only shown by particles larger than about 2 nm ° Mdssbauer spectroscopy showed a platinum particle with 309 atoms to have the normal fee structure,but palladium-platinum particles suffered electron-beam-induced change from fee to cph. ... 

The nature of acid sites was at the center of several studies. Barthomeuf discussed spectroscopic methods applied to study hydroxyl groups, Bronsted and Lewis acidities and basicities, and the effects of extraframework oxides on acidity or basicity. These are IR, which is the most important here, NMR, XPS, UV- and visible, Raman and Mdssbauer spectroscopies. Far infrared technique may reveal cation locations. The shift of the band associated with the NH of pyrrole depends on the charge of 0, which in turn determines the basicity. Some progress has been made in the last few years in the identification of different OH groups. An interesting observation was that sU adsorbed benzene molecules are disturbed by the 0-s, even at high benzene coverages. 

Mossbauer spectroscopy is based on the Mossbauer effect discovered by Rudolf Mdssbauer (Mossbauer 1958a, b). The discovery was honored by the Nobel Prize in 1961. 

Mdssbauer RL (1958a) Z Physik 151 124 Mossbauer RL (1958b) Naturwissenschaften 45 538 Mossbauer RL, Wiedemann W (1960) Z Physik 159 33 Mossbauer RL, Parak F, Hoppe W (1981) In Gonser U (ed) Mossbauer spectroscopy II - the exotic side of the method. Springer, Berlin Moshkovskii Yu Sh (1968) In Goldanskii VI, Herber RH (eds) Chemical applications of Mossbauer spectroscopy, Academic, New York and London Muir A, Ando KJ, Coogan HM (1958-1965) MOssbauer effect data index. Inter Science, New York, London, Sydney... 

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