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Abstract  

127I Mössbauer spectra for the phenyliodonium ylides were measured at 20 K. The valence electron populations (Ns, Nx-z) and the charge number (ZI) for iodine atom are estimated from the Mössbauer parameters. The obtained populations were very close to those of diphenyliodonium chloride having two I-C primary bonds. To examine the possibility of some double bond character, the electron populations for the case of Nz = 1.90 are estimated. In this case, the ZI values become larger as 1.2-1.3, and these values were unreasonably large because the values are close to those of PhICl2, PhI(OAc)2 having electron withdrawing ligands. Thereby, 127I Mössbauer parameters suggest little double bond character for phenyliodonium ylides.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Yu D. Perfiliev
,
V. S. Rusakov
,
L. A. Kulikov
,
A. A. Kamnev
, and
K. Alkhatib

Summary  

Resonant lines observed in source experiments are usually significantly broader thanthosein the corresponding absorber experiments. In order to explain this phenomenon, the model of a trapped electron has been proposed. Auger electrons emitted, for instance, after electron capture by 57Со or after the converted isomeric transition of119mSn, as well as secondary electrons, may be trapped in the vicinity of the nucleogenic ion. An asymmetric distribution of quadrupole splittings in the resulting emission Mössbauer spectra is thus a consequence of electron capture by lattice traps located at different distances from the daughter ion. Estimates of quadrupole splitting values, which may be causedby trapped electrons located at different distances from the nucleogenic atom, support the above mentioned model.

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Abstract  

Mössbauer spectra of hexakis/alkylurea/iron/III/ complexes were measured to investigate the paramagnetic relaxation in ionic compounds. The effects of iron-iron distance and temperature on Mössbauer line shape were studied in these compounds, and the results are discussed in comparison with our previous data on tris/\-diketonato/iron/III/.

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Abstract  

Mössbauer spectra of (Fe0.5Zn0.5)PS3, which is isomorphous with FePS3, were measured at 300 and 80 K, and were compared with those of FePS3. We succeeded in preparing (Fe0.5Zn0.5)PS3 intercalated with pyridine. In the XRD pattern of the intercalate the diffraction peaks corresponding to (Fe0.5Zn0.5)PS3 were completely missing, suggesting that the intercalation was completely performed with pyridine. The Mössbauer spectra were changed significantly by the intercalation suggesting the charge transfer from guest molecules to the host matrix. The replacement of iron by zinc has no influence on the electronic state of the iron atom, except for the magnetic interaction.

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Abstract  

155Gd Mössbauer spectra of some Gd(III)-b-diketonato complexes are reported. All of their 155Gd Mössbauer isomer shift (d) values fall in a narrow range of +0.55-+0.65 mm.s-1, and are between those of GdF3 and the cubic form of Gd2O3. This indicates that their Gd-O bonds have small covalent character. The value for quadrupole coupling constant (e2qQ) spread out from 1.67 to 7.56 mm.s-1 and reflects the difference well in symmetry of the coordination polyhedron around Gd(III) ions for those Gd(III)-b-diketonato complexes.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
T. Saito
,
J. Wang
,
T. Kitazawa
,
M. Takahashi
,
M. Takeda
,
M. Nakada
,
T. Nakamoto
,
N. Masaki
,
T. Yamashita
, and
M. Saeki

Abstract  

Four types of neptunyl(VI) hydroxides have been synthesized by chemical oxidation of Np(IV) instead of ozone oxidation of Np(V) which caused the partial oxidation to the heptavalent state. NpO2(OH)2 (I) and NpO2(OH)2·H2O (orthorhombic type) (II) have been obtained by adding pyridine to the solution at 373K and 343K, respectively. NpO2(OH)2·H2O (hexagonal type) (III) and NpO2(OH)2·xH2yNH3 (x+y=1) (IV) have been prepared by using LiOH and NH4OH, respectively. The four materials have been characterized by X-ray powder diffraction patterns, thermogravimetric analysis and237Np Mössbauer spectra. The237Np Mössbauer spectrum of (I) measured first time as anhydrous neptunyl(VI) hydroxide (δ=−46.2 mm/s,e 2 qQ=193 mm/s and η=0.16 at 4.8K) has more distinct five-line Mössbauer pattern than those of (II), (III) and (IV). The Mössbauer spectra for (II), (III) and (IV) are slightly different from each other. The structural information has been obtained from these data.

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Abstract  

Asymmetry of the relative line intensities in the57Fe. Mössbauer spectra of powdered samples of Na3[Fe/CN/5NH3]3H2O is reported. It is shown that the effect is due to a prefered orientation of the electric field gradient /EFG/, which is assumed to have a conical distribution around the normal of the absorber plane. Using this model for the EFG distribution the angle between the EFG and the normal of the absorber plane is determined.

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Abstract  

Five neptunyl(V) compounds were synthesized and studied by237Np Mössbauer spectroscopy. The isomer shifts (δ) of the Mössbauer spectra ranged from −18.6 to −19.1 mm/s for the compounds with Np atoms surrounded by 7 oxygen atoms (coordination number (CN) 7). On the other hand, the larger value of δ was obtained for the compound with CN 8. from the comparison of the present results with those reported on neptunyl(V) and (VI) compounds, it is concluded that there is a correlation between the δ and the CN for neptunyl(V) compounds, and the distribution of δ is narrower for neptunyl(V) compounds than that of neptunyl(VI) compounds.

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Abstract  

121Sb Mössbauer spectra of the title complexes, whose isomer shifts are intermediate between the organoantimony(III) and organoantimony(V) compounds, suggest that considerable electrons are donated from hydrido ligand and Fe(CO)4 fragments to the antimony atom.

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Abstract  

Mössbauer spectra of low-spin ferric and high-spin ferrous compounds may be sensitive to the local humidity during the measuring process or to other parameters associated with the hydration degree of the sample. This effect is related to the location of water molecules around the t2g orbitals (dxy, dxz, dyz). The results indicate that for comparative studies all Mössbauer measurements must be carried out in well standardized conditions.

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