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arXiv 2102.11308astro-ph.SRastro-ph.GA
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改进的UV和Hf II的原子跃迁几率及两颗贫金属星中Hf能级的测定

Improved Atomic Transition Probabilities for UV and Optical Lines of Hf II and Determination of the Hf Abundance in Two Metal-Poor Stars

E. A. Den Hartog, J. E. Lawler, I. U. Roederer

备注：
Accepted for publication in the Astrophysical Journal Supplement Series (32 pages, 4 figures, 4 tables)
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摘要：

我们报告新的分支分数测量199紫外和光学跃迁的铪II。这些跃迁的波长（波数）范围为2068- 6584 A（48322-15183 cm-1），起源于17个奇宇称上能级，能量范围为38578-53227 cm-1。分支分数与辐射寿命相结合，在早期的研究中报告产生一组跃迁概率和log（gf）值，精度范围从5- 25%。比较是从文献中存在这样的数据的转移概率。我们使用这些新的过渡概率得到改善铪丰度在两个贫金属恒星。HD 196944在s过程元素中得到增强，我们从12条Hf II线中推导出log Hf（Hf）= -0.72 +/-0.03（sigma = 0.09）。HD 222925在r过程元素中得到增强，我们从20条Hf II线中推导出log Hf（Hf）= 0.32 +/- 0.03（σ = 0.11）。这些测量极大地扩展了在UV和光学光谱中用于分析的潜在有用的Hf II线的数量。

英文摘要：

We report new branching fraction measurements for 199 UV and optical transitions of Hf II. These transitions range in wavelength (wavenumber) from 2068- 6584 A (48322-15183 cm-1) and originate in 17 odd-parity upper levels ranging in energy from 38578-53227 cm-1. The branching fractions are combined with radiative lifetimes reported in an earlier study to produce a set of transition probabilities and log(gf) values with accuracy ranging from 5-25%. Comparison is made to transition probabilities from the literature where such data exist. We use these new transition probabilities to derive improved Hf abundances in two metal-poor stars. HD 196944 is enhanced in s-process elements, and we derive log epsilon (Hf) = -0.72 +/- 0.03 (sigma = 0.09) from 12 Hf II lines. HD 222925 is enhanced in r-process elements, and we derive log epsilon (Hf) = 0.32 +/- 0.03 (sigma = 0.11) from 20 Hf II lines. These measurements greatly expand the number of potentially useful Hf II lines for analysis in UV and optical spectra.

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