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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  

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  

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  

Mechanisms of chemical reactions initiated by recoil implantation were studied in the systems51Cr+M/acac/3 51Cr/acac/3 where M is a trivalent metal. The yield of51Cr/acac/3 increased linearly with an increase of inverse of the force constant of metal-oxygen bonding K(M–O). This indicates that there is competition between the implanted51Cr atom and M. However, exception for this trend was the case of Co/acac/3 catcher, for which the yield of51Cr/acac/3 was much higher than that expected for a competition reaction. Complex features of the replacement reaction caused by implantation are discussed in this system.

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Abstract  

Neutron induced prompt gamma-ray activation analysis (PGAA) is applied for determining boron contents in volcanic rocks, which is an important element in the discussion of material circulation in volcanic arc systems. To evaluate the recycling of oceanic crust in Kyushu, we analyzed boron and other trace element contents in basaltic rocks from the area. The basalts from volcanic front have high B/Nb (2.9–3.7), B/Zr (0.1–0.2) and B/Sm (2.8–6.0) ratios, whereas those ratios in the basalts from backarc are extremely low (<0.5; <0.1; 0.5–1.7), respectively. This indicates that the recycling of subducted oceanic crust to the arc crust is limited in the volcanic front.

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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  

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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Abstract  

In order to estimate the source in pelagic sediments, principal component analysis (PCA) was applied to the data matrix which was made by chemical compositions of sediments measured by instrumental neutron activation analysis (INAA) and prompt gamma-ray analysis (PGA). The results of PCA represented 3-factor models in each sediment, explaining 58–98% of the total variations in the sediments. A comparison of eigenvectors of terrigenous elements indicated the existence of 2 sources. Group 1 is suggested to be continental dust, whereas Group 2 is suggested to be volcanic rock. Variation of K/Ti ratio and Eu anomaly of sediments supported the above results.

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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  

Characterization of Fe3/CO/12 cluster adsorbed on -Al2O3 and SiO2 was undertaken by means of57Fe-Mössbauer spectroscopy. In the case of Fe3/CO/12 adsorbed on -Al2O3, iron atoms were found to be similar to metallic iron. Fe3/CO/12 adsorbed on SiO2 retains its original molecular structure and chemical nature.

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