p-核種の生成とその同位体比異常

概要

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The origin of p-isotopes (proton rich isotopes) and their isotopic anomalies are reviewed in this article. The p-isotopes (^<84>Sr, ^<124>Xe, ^<130>Ba, ^<144>Sm, ^<196>Hg, etc.) are heavy isotopes (A≧74) which cannot be synthesized by s-process or r-process. The p-isotopes are considered to be produced by the transmutation of heavy elements into lighter p-isotopes via a series of (γ, n), (γ, p) and (γ, α) reactions in supernovae. We can constrain the site and the condition of nucleosynthesis in supernovae from abundances of the p-isotopes. The isotopic anomalies of the p-isotopes of Xe, Cd and Sn are found in acid residues of the Allende carbonaceous chondrite. The anomalies of ^<84>Sr and ^<144>Sm are also found in the Allende FUN inclusions. They are considered to be presolar origin. The anomalies of ^<196>Hg are found, however, their origin still remains enigmatic. The anomaly of Mo isotopic abundances is found in the Sikhote-Alin iron meteorite. The anomaly can be explained by (γ, n) reaction chains of Mo. The further study of the Mo anomaly will give us interesting informations not only about the p-process, but also about the r-process effect on ^<93>Nb, the double β-decay of ^M96>Zr, and the (γ, n) reaction chain of ^<99>Tc.
日本地球化学会の論文
1992-09-24