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  • Author or Editor: Y. Ohkubo x
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Abstract  

It was found that not only111mCd but also105Ag and106mAg sublimate at 1050 °C under a reduced pressure from Pd foils irradiated with -particles. The sublimation method has enabled rapid separation of the isotopes and repeated use of valuable Pd foils. Adsorption onte -Fe2O3 and coprecipitation with ferric hydroxide were studied by using radioactive tracers.

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Abstract  

The time-differential perturbed angular correlation (TDPAC) method was applied to a study on the behavior of 140Ce atoms implanted in highly oriented pyrolytic graphite (HOPG). Exponential-type gradual attenuation of the directional anisotropy of the relevant γ-ray cascade was observed in the perturbation patterns. From temperature dependence of the relaxation rate, a thermally activated dynamic motion of the probe atoms was suggested.

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Abstract  

Bombardment conditions, chemical separation, and counting method were examined for routine determination of carbon, nitrogen, and oxygen in various matrices by charged-particle activation analysis with respect to reliability, reproducibility, simplicity, and rapidity. A system was then set up for trustworthy measurement of these elements.

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Abstract  

We made systematic studies of lanthanoid metallofullerenes on the following three properties using the radiochemical method: (1) the relative production yields of metallofullerene species, (2) variation of the HPLC retention time among M(III)@C82 species, and (3) the effects of the reactor irradiation on the survival yields of each metallofullerene species. The production yields of M@C82 relative to La@C82 were found to decrease as the atomic number of M became larger and as the number of atom ratio, M/C, in the carbon rod became larger. On the other hand, the production yields of M1M2@C82, relative to that of LuM@C82 were found to increase for the larger atomic number. The retention time for the M(III)@C82 species in the Buckyprep column was found to become slightly longer for the larger atomic number but it becomes abruptly larger for Gd, and Tb by about 5%. The overall effects of the reactor irradiation on the survival yields (or retention yields) of M@C82 species were found to be (19.7±2.1)%.

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Abstract  

Transport and distribution of metal ions in rice and soybean plants were studied using multitracers produced by irradiating an Au target by 135 MeV/nucleon12C,14N, or16O ions accelerated by RIKEN Ring Cyclotron. The multitracer consisted of radioisotopes of the following elements: Be, Na, Sc, Mn, Fe, Co, Zn, Se, Rb, Sr, Y, Zr, Nb, Ag, Te, Ba, Ce, Pm, Eu, Gd, Tb, Tm, Yb, Lu, Hf, Ir, and Pt. Rice and soybean plants were grown in a nutrient solution and also on soil containing a multitracer. -ray spectroscopy of different parts of the plants showed that all the elements were more or less taken up by roots, while appreciable transport to leaves and seeds was observed only for Mn, Zn, Se, Rb, Sr, and Ba.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: F. Ambe, Y. Ohkubo, S. Ambe, Y. Kobayashi, T. Okada, Y. Yanagida, J. Nakamura, K. Asai, Y. Kawase, and S. Uehara

Abstract  

The features of time-differential perturbed angular correlation (TDPAC) in studies on local chemical structures around impurity atoms are described in comparison with those of Mössbauer emission spectroscopy with four typical examples of recent applications to metal oxide systems, namely,99Rh 99Ru in -Fe2O3 and YBa2Cu3O7– and117Cd 117In in MO (M=Mn, Co, Ni) and BaRu2/3Cd1/3O3.

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Abstract  

Nuclear reactions of165Ho induced by 1.0 GeV15N or 1.8 GeV14N ions and those of141Pr induced by 2.3 GeV or 3.8 GeV40Ar ions have been studied by off-line -ray spectrometry. Mass distributions of the products were confirmed to reveal a limiting characteristics at projectile energies beyond 2 GeV. Longitudinal momentum transfer was measured with a thick-target-thick-catcher technique. The results demonstrated that a provisional limiting of the recoil velocity appears in the energy range of 2–10 GeV, besides the ultimate limiting condition already pointed out. The coincidence in the onset energy of the limiting behavior was interpreted as the result of the existence of the limit heating of nucleus.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: S. Ambe, S. Chen, Y. Ohkubo, Y. Kobayashi, H. Maeda, M. Iwamoto, M. Yanokura, N. Takematsu, and F. Ambe

Abstract  

We established Multitracer, a new versatile radiotracer technique, for simultaneous tracing of a number of elements in various chemical, environmental, and biological systems. Metal foil targets (typically Au, Ag, Ge, Cu and Fe) are irradiated with C, N, or O ions accelerated up to 135 MeV/nucleon by RIKEN Ring Cyclotron. Radiochemical procedures have been developed to remove the target material leaving the nuclides as Multitracer solutions containing various radionuclides of Be, Na, Mg, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Te, I, Ba, Ce, Pm, Eu, Gd, Tb, Tm, Yb, Lu, Hf, W, Re, Os, Ir, Pt, and Hg. Multitracers enable efficient tracing of a number of elements, and comparison of their behavior under strictly identical experimental conditions. Such features will be demonstrated by means of an example of application to a model experiment for the study of removal mechanism of various elements from the ocean.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: W. Sato, K. Sueki, K. Kikuchi, K. Kobayashi, S. Suzuki, Y. Achiba, H. Nakahara, Y. Ohkubo, F. Ambe, and K. Asai

Abstract  

Time-differential perturbed angular correlation method was applied to Ce@C82 in order to investigate the electronic properties of the encaged Ce atom. The nuclear quadrupole frequency of the nuclear spin of the Ce was successfully determined as ωQ = 6.5(3)·107 rad/s, which is much greater than what has already been estimated for Ce4+ and La3+ in other compounds. By comparing the present value with the values for the Ce4+ and La3+, it was inferred that the valence state of the encaged Ce atom is trivalent.

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