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An Attempt for determining $$^{235}$$U/$$^{238}$$U ratio for a trace amount of uranium: Search for an extinct radionuclide $$^{247}$$Cm in the early solar system

Chai, J.; Miyamoto, Yutaka; Kokubu, Yoko; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu; Oura, Yasuji*; Ebihara, Mitsuru*

$$^{247}$$Cm is an important nuclide because it has the next-shortest half-life (1.6$$cdot$$10$$^{7}$$ yr) from $$^{244}$$Pu among the transuranic nuclides. The disintegration of $$^{247}$$Cm to $$^{235}$$U by three $$alpha$$ decays and two $$beta$$ decays and the chemical fractionation between Cm and U during the formation of solid materials in early solar system lead to changes in the ratios of $$^{235}$$U to $$^{238}$$U. This variation may provide strict constraints on the time interval between the last r-process nucleosynthetic event and the formation of the solar system. It is important to develop a practical analysis protocol to determine the isotope ratio of trace uranium in geochemical and environment samples. As uranium is the least abundant element in our solar system, analytical techniques with high sensitivity and precision are required. In this study, a double focusing inductively coupled plasma mass spectory was applied to measure isotopic ratio of uranium. By one set data obtained from the EDTA phase of the Jilin meteorite sample, the upper limit of $$^{247}$$Cm in the early solar system was calculated and $$^{247}$$Cm/$$^{235}$$U $$<$$ 0.003 was obtained.



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Category:Chemistry, Analytical



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