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Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh
Published on: May 3, 2019
RETRACTED: 測定された146Sm半減期の短縮と,太陽系における146Sm-142Nd年代表への影響
N Kinoshita1, M Paul, Y Kashiv
1Research Facility Center for Science and Technology, University of Tsukuba, Tsukuba, Japan.
まとめ
初期の太陽系イベントの年代測定の鍵となる同位体であるサマリウム-146 (146Sm) の半減期は,6800万年に修正されました. この発見は,より早い,より短い惑星の微分化タイムラインを示唆しています.
科学分野:
- * 核天体物理学と地球化学.
- * 放射線年代測定と宇宙化学.
- * 同位体地質学と惑星科学.
背景:
- * 絶滅した放射性核酸サマリウム-146 (146Sm) は,その子産物ネオジミウム-142 (142Nd) を通して,初期の太陽系物質の年代測定に不可欠である.
- * 正確な半減期と146Smの初期豊富さは,正確な時間的解釈のために不可欠です.
- * 146Smの半減期と初期豊富さの以前の推定は,初期の太陽系年代表に不確実性をもたらしました.
研究 の 目的:
- * アルファ活性と原子比測定を用いてサマリウム146 (146Sm) の半減期を精製する.
- * 太陽系初期における146Smの初期濃度を再計算する.
- * 改訂された146Smデータを用いて,惑星マントルの分化イベントのタイミングを再評価する.
主な方法:
- *サマリウム-146 (146Sm) とサマリウム-147 (147Sm) のアルファ活性比の分析.
- *サマリウム-146 (146Sm) とサマリウム-144 (144Sm) の原子比の決定.
- * 146Sm142Nd同位体系を地球,月,火星のサンプルの年代測定に用いること.
主要な成果:
- * サマリウム-146 (146Sm) の半減期は68±700万年と決定され,以前から認められていた値より大幅に短かった.
- *初期の太陽系における146Smの初期濃度 (146Sm/144Sm) は0.0094 ± 0.0005.0と推定されている.
- *146Sm142Ndを用いた惑星のシリケートマントルの分化イベントの年代測定は,より早い,より短い時間帯を示しています.
結論:
- * サマリウム-146 (146Sm) の半減期と初期濃度の改定により,初期の太陽系年代順に調整が必要となる.
- * 惑星の分化プロセスは,以前考えられていたよりも,圧縮された,早期のスケールで発生しました.
- * この研究は,地上の惑星と太陽系の初期進化を理解するために,より正確な同位体クロノメーターを提供します.
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