Improved192,194,195,196Pt(n,γ) and192Ir(n,γ) astrophysical reaction rates
Improved192,194,195,196Pt(n,γ) and192Ir(n,γ) astrophysical reaction rates
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提高192、194、195、196Pt(n,γ)和192Ir(n,γ)天体物理反应速率
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
K. H.Guber
中科院分区：
文献类型：
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作者：
P. Koehler;K. H.Guber
铂完全是由慢中子俘获(S)核合成过程产生的，因此这种核素的准确(n，伽马)反应速率将允许将其用作接近S核合成过程终止的重要校准点。为此，我们在橡树岭电子直线加速器上测量了从10 eV到几百keV能量范围内的中子俘获和总截面。对其他铂同位素的测量在一定程度上是因为只有相对较小的适度浓缩的铂样本。从这些数据计算出天体物理的$%^{192,194,195,196}$铂($n，伽马$)反应率，精度约为3%-5%。之前还没有公布过这些同位素的准确反应速率。在现有的{S}工艺温度下，以前推荐的速率比我们的新速率大(高达35%)，并且具有与温度函数显著不同的形状。我们使用我们的新的铂结果，以及$^{191,193}$Ir(n，$%伽马$)数据来校准核统计模型计算，从而获得了对未测量的{S}过程分支点同位素$^{192}$Ir的改进速率。
$^{192}$Pt is produced solely by the slow neutron capture ( extit{s}) nucleosynthesis process and hence an accurate ($n$,$gamma $) reaction rate for this nuclide would allow its use as an important calibration point near the termination of the extit{s}-process nucleosynthesis flow. For this reason, we have measured neutron capture and total cross sections for $% ^{192,194,195,196,nat}$Pt in the energy range from 10 eV to several hundred keV at the Oak Ridge Electron Linear Accelerator. Measurements on the other Pt isotopes were, in part, necessitated by the fact that only a relatively small $^{192}$Pt sample of modest enrichment was available. Astrophysical $% ^{192,194,195,196}$Pt($n,gamma $) reaction rates, accurate to approximately 3%--5 %, were calculated from these data. No accurate reaction rates have been published previously for any of these isotopes. At extit{s}-process temperatures, previously recommended rates are larger (by as much as 35%) and have significantly different shapes as functions of temperature, than our new rates. We used our new Pt results, together with $^{191,193}$Ir(n,$% gamma $) data, to calibrate nuclear statistical model calculations and hence obtain an improved rate for the unmeasured extit{s}-process branching-point isotope $^{192}$Ir.