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  • Author or Editor: H. Sano x
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Abstract  

Absorption Mössbauer spectra of high-spin57Fe(acac)3 incorporated in diamagnetic Co(acac)3 and in paramagnetic Mn(acac)3 and of the γ-ray irradiated (57Fe, Co) (acac)3 and (57Fe, Mn) (acac)3 were compared with emission spectra of57Co-labelled Co(acac)3. Magnetic hfs is found in the spectra of (57Fe, Co) (acac)3 at 78 to 195 K, whereas such hfs is observed neither for the spectrum of57Co-labelled Co(acac)3 nor for that of γ-ray irradiated (57Fe, Co) (acac)3). The absence of magnetic hfs in the spectrum of diamagnetic57Co-labelled cobalt(III) compounds was ascribed to the spin-spin interaction due to the radicals produced in the vicinity of the decayed atom.

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Abstract  

Time resolved Mössbauer spectra were measured for57Co-labelled Co/IO3/2 using a delayed coincidence technique. A life-time for unstable57Fe(II)-species formed through EC-decay was estimated to be 43±5 ns at room temperature and the initial distribution of57Fe(II)/57Fe(III) at 14.4 keV nuclear level to be 0.47±0.13. The results are discussed in terms of electron transfer from the decayed57Fe(II) atoms to iodate ions.

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Abstract  

Emission Mössbauer spectra of mixedvalence trinuclear complexes,57Co-labelled [CoFe2O(CH3CO2)6(H2O)3] and [CoFe2O(CH3CO2)6 (py)3]py were compared with that of [CoCr2O(CH3CO2)6 (py)3]py. It was found that the57Fe atoms produced in57Co-labelled [CoFe2O(CH3CO2)6(H2O)3] and [CoFe2O(CH3CO2)6 (py)3]py showed a temperature-dependent mixed-valence state as observed in the absorption Mössbauer spectra of [Fe3O(CH3CO2)6 (H2O)3] and [Fe3O(CH3CO2)6 (py)3]py, respectively, while57Co-labelled [CoCr2O(CH3CO2)6 (py)3]py showed a temperature-independent divalent iron/II/ state. The results indicate that the decayed atoms keep their position at the sites of original57Co atoms and that the valence electrons are transferred through the intramolcular bondings.

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Abstract  

Reaction products of [2]ferrocenophane with CF3COOH, CCl3COOH, CF3SO3H and SbCl5 were prepared. Mössbauer spectroscopic data and magnetic susceptibility measurements suggest the bond formation of Fe–H+ and Fe–Cl+, in which iron atoms are in a high-spin Fe/II/state.

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Abstract  

Positron-lifetime and Doppler-broadened spectra were measured for ion-exchanged (Na+, Zn2+, Al3+, Cu2+ and alkylammonium) montmorillonites (mont). The line-shape parameters of the spectra for alkylammonium-intercalated monts were almost equal to those observed for the corresponding alkylammonium salts used for the intercalation. Upon exchange of diamagnetic ions in the interlayer spaces of mont for paramagnetic Cu2+ ions, the longest-lived component ascribed to ortho-positronium (Ps) was shortened from ca 1 to 0.62 ns, and the Doppler-broadened spectrum was narrowed. These results demonstrate that Ps atoms are predominantly distributed in the interlayer spaces of mont, rather than in the aluminosilicate layers.

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Abstract  

Mixed-metal cubane-type clusters of [Mo3FeS4(NH3)9(H2O)Cl4 and [Mo3FeS4(H2O)10](pts)4.7H2O have been characterized by means of57Fe-Mössbauer spectroscopy. The Mössbauer parameters indicate that the oxidation states of iron in the cluster compounds are ascribed to +2.54 and +2.39, respectively.

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Abstract  

KX-ray-gated emission Mössbauer spectra of57Co-labelled CoF2 and CoF2.2H2O were measured at room temperature, using the coincidence technique. A difference was found in the relative intensity of57Fe(II)/57Fe(III) between the X-ray-gated and non-gated emission spectra. The results are explained in terms of local radiolytic effects of water of crystallization and the chemical effects associated with the de-excitation processes caused by EC-decay.

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Abstract  

Mixed-valence states of57Fe-atoms produced after EC-decay of57Co in oxo-centered trinuclear cobalt-iron carboxylates have been studied by means of emission Mössbauer spectroscopy. The emission Mössbauer spectra show nearly the same temperature dependence of the mixed-valence state as found in the absorption Mössbauer spectra of the corresponding trinuclear iron carboxylates. The results indicate that most of the decayed atoms keep their position at the sites of original57Co atoms.

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Abstract  

The crystal structures of oxo-centered trineclear cobalt-iron chloroacetate complex [CoIIFe 2 III O(CH2ClCO2)6(H2O)3]·3H2O (1) was compared with that of previously reported trinuclear iron complex [FeIIFe 2 III O(CH2ClCO2)6(H2O)3]·3H2O (2) which has an isomorphous structure to 1. Compound 1 crystallizes in space group P21/n with Z=4 in a unit cell of a=14.826 (4) Å, b=4.536 (8) Å, c=14.000 (4) Å, =100.32 (2)0 and V=2968 (11) Å3. The structure was refined to R=0.75 and Rw=0.82. The coordination geometries of the three iron atoms are observed equivalent in 1 indicating a static disorder of the position among cobalt and iron atoms. Two distinct FeIII doublets observed in Mössbauer spectra of 1 become an indistinguishable broad doublet by dehydration of crystal water. On the other hand, no significant line-broadening is observed after the dehydration in complex 2. The results indicate that the dehydration in 2 induces a local environmental change reordering of an electronic configuration around iron atoms, whereas the remaining disordering is reflected in Mössbauer spectrum after the dehydration in 1.

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Abstract  

Coincidence Mössbauer spectra of57Co-labelled [CoFe2O(CH3CO2)6(H2O)3] were determined at 78 K and 298 K with three timewindows of 0–50, 50–150 and 150–300 ns. Temperature dependence in the spectral shape ascribed to an intramolecular electron transfer was observed in all the time-window spectra, while little time dependence was observed. The results indicate that57Fe atoms produced by EC-decay are incorporated in a chemical environment similar to that of the parent57Co atoms, forming a trinuclear FeIIFe2 III structure at an early stage after the EC-decay.

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