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arXiv 1310.3231nucl-exastro-ph.EP
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~（33）S（α，p）~（36）Cl截面的测量：早期太阳系中~（36）Cl产生的意义

Measurement of the 33S(α,p)36Cl cross section: Implications for production of 36Cl in the early Solar System

Matthew Bowers, Yoav Kashiv, William Bauder, Mary Beard, Philippe Collon, Wenting Lu, Karen Ostdiek, Daniel Robertson

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摘要：

已知寿命τ< 100 Ma的短寿命放射性核素在45亿年前太阳系形成时就已经存在。确定SLR的来源对于理解太阳系形成的时间尺度和历史早期发生的过程非常重要。熄灭的36 Cl（t_1/2 = 0.301 Ma）被认为是由年轻太阳发射的太阳高能粒子（SEP）与新生太阳系中的气体和尘埃相互作用产生的。然而，计算早期太阳系（ESS）SLR产生的模型缺乏36 Cl产生反应的实验数据。我们在这里首次测量了36 Cl主要生成反应之一33 S（α，p）36 Cl的截面，能量范围为0.70 - 2.42 MeV/A。截面测量通过轰击靶并收集反应中产生的反冲的36 Cl原子，化学处理样品，并用加速器质谱（AMS）测量活化样品的36 Cl/Cl比来进行。实验结果被发现是系统高于截面在以前的局部照射模型和其他豪泽-Feshbach计算的预测。然而，实验测量的截面对早期太阳系中36 Cl的模拟产生的影响被发现是最小的。涉及S靶的反应通道主导36 Cl的产生，但天体物理事件参数可以显著改变每个反应的相对贡献。

英文摘要：

Short-lived radionuclides (SLRs) with lifetimes τ< 100 Ma are known to have been extant when the Solar System formed over 4.5 billion years ago. Identifying the sources of SLRs is important for understanding the timescales of Solar System formation and processes that occurred early in its history. Extinct 36Cl (t_1/2 = 0.301 Ma) is thought to have been produced by interaction of solar energetic particles (SEPs), emitted by the young Sun, with gas and dust in the nascent Solar System. However, models that calculate SLR production in the early Solar System (ESS) lack experimental data for the 36Cl production reactions. We present here the first measurement of the cross section of one of the main 36Cl production reactions, 33S(α,p)36Cl, in the energy range 0.70 - 2.42 MeV/A. The cross section measurement was performed by bombarding a target and collecting the recoiled 36Cl atoms produced in the reaction, chemically processing the samples, and measuring the 36Cl/Cl ratio of the activated samples with accelerator mass spectrometry (AMS). The experimental results were found to be systematically higher than the cross sections used in previous local irradiation models and other Hauser-Feshbach calculated predictions. However, the effects of the experimentally measured cross sections on the modeled production of 36Cl in the early Solar System were found to be minimal. Reactions channels involving S targets dominate 36Cl production, but the astrophysical event parameters can dramatically change each reactions' relative contribution.

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