Isotope fractionation due to sedimentation of atoms in centrifuged indium-lead alloy

Ono, Masao  ; Iguchi, Yusuke*; Okayasu, Satoru  ; Esaka, Fumitaka  ; Kobayashi, Katsura*; Hao, T.; Bagum, R.*; Osawa, Takahito  ; Fujii, Kimio; Nakamura, Eizo*; Mashimo, Tsutomu

The atomic-scale graded structure of In-Pb alloy was formed by an ultracentrifuge experiment under conditions that a gravitational field of 0.8110 G for 100 hours at 150 C in solid state in our previous study. The isotope ratio measurements were performed on the centrifuged sample with secondary ion mass spectrometer (SIMS). Pb/Pb and Pb/Pb isotope ratio changed with negative gradient in the direction of centrifugal force approximately 1.5% and 0.8%, respectively. And three-isotope diagram of Pb/Pb versus Pb/Pb proved that the isotope fluctuation depends on isotopic mass difference. These results showed that the strong gravitational field not only affected on the inter-diffusion but also on self-diffusion in this alloy as causing isotope fractionation effect, and the isotope fractionation was dependent on mass-difference.