高温Tl衰变解释了太阳系早期的Pb年代
Guy Leckenby1,2, Ragandeep Singh Sidhu3,4,5, Rui Jiu Chen6,7,8
1TRIUMF, Vancouver, British Columbia, Canada. guy.leckenby@gmail.com.
Nature
|November 13, 2024
概括
使用-205 (Pb-205) 的放射性年代测定有助于确定太阳的诞生环境. 新的核衰变测量提供了准确的Pb-205产量,
科学领域:
- 核天体物理学
- 宇宙化学
- 恒星核合成
背景情况:
- 石中长期存在的放射性核可以帮助我们了解太阳的形成和核合成.
- -205 (Pb-205) 通过缓慢的中子捕获 (s-过程) 在非对称巨分支 (AGB) 恒星中合成,但其丰度预测受到不确定的衰变率的限制.
- 对于Pb-205和-205 (Tl-205) 的精确衰变速率对于了解太阳系早期的时间表至关重要.
研究的目的:
- 在恒星温度下限制Pb-205和Tl-205的衰变速度.
- 为了确定太阳物质在母分子云中的隔离时间.
- 为了验证Pb-205/Tl-205衰变系统作为太阳系早期的计时器.
主要方法:
- 首次测量了完全电离的Tl-205 (Tl-205^81+) 的结合状态β减衰变.
- 使用实验约束的衰变速率的 AGB 恒星模型来计算 Pb-205 的产量.
- 集成的星系化学进化 (GCE) 模型,计算了产量和石同位素比率 (Pb-205/Pb-204),以确定隔离时间.
主要成果:
- 测量Tl-205^81+的半衰期是理论估计的4. 7倍,实验不确定性为10%.
- 使用实验验证的衰变率计算了新的Pb-205产量.
- 确定了积极的隔离时间,与早期太阳系中其他短寿命的放射性核相一致.
结论:
- 这项研究解决了预测Pb-205丰度的核物理主要局限性.
- 这些发现支持太阳在长期存在的巨大分子云中诞生.
- Pb-205/Tl-205衰变系统被证实是早期太阳系的一个有价值的计时器.
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