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arXiv 0809.2757astro-ph
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高分辨率中子俘获和总截面测量及s过程温度下~(95)Mo(n,γ)反应速率

High-Resolution Neutron Capture and Total Cross-Section Measurements, and the Astrophysical 95Mo(n,gamma) Reaction Rate at s-process Temperatures

P. E. Koehler, J. A. Harvey, K. H. Guber, D. Wiarda

摘要:

钼同位素丰度的恒星模型预测的S过程中,除了95钼,在很好的协议与数据从单粒主流前太阳SiC。由于陨石的数据似乎是合理的,并且没有对恒星理论进行合理的修正,导致95 Mo的一致性很好,因此有人建议该核素的中子捕获反应速率低了30%。因此,我们已经作出了一个新的测定95 Mo(n,γ)反应速率通过高分辨率测量的中子俘获和总截面的95 Mo在橡树岭电子直线加速器。这些数据进行了分析与R-矩阵代码SAMMY获得共振参数En = 10千电子伏。此外,对我们的捕获设备进行的一个小的改变使我们能够采用一种新技术来大大改善共振自旋和宇称分配。这些新的共振参数,连同我们的数据在未解决的范围内,被用来计算95 Mo(n,γ)反应速率在s-过程温度。我们将目前推荐的速率与我们的新结果进行比较,并讨论它们对天体物理学的影响。

英文摘要:

Abundances of Mo isotopes predicted by stellar models of the s process are, except for 95Mo, in good agreement with data from single grains of mainstream presolar SiC. Because the meteorite data seemed sound and no reasonable modification to stellar theory resulted in good agreement for 95Mo, it has been suggested that the recommended neutron capture reaction rate for this nuclide is 30% too low. Therefore, we have made a new determination of the 95Mo(n,gamma) reaction rate via high-resolution measurements of the neutron-capture and total cross sections of 95Mo at the Oak Ridge Electron Linear Accelerator. These data were analyzed with the R-matrix code SAMMY to obtain parameters for resonances up to En = 10 keV. Also, a small change to our capture apparatus allowed us to employ a new technique to vastly improve resonance spin and parity assignments. These new resonance parameters, together with our data in the unresolved range, were used to calculate the 95Mo(n,gamma) reaction rate at s-process temperatures. We compare the currently recommended rate to our new results and discuss their astrophysical impact.

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