Improved Laboratory Transition Probabilities for Hf II and Hafnium Abundances in the Sun and 10 Metal-poor Stars
Improved Laboratory Transition Probabilities for Hf II and Hafnium Abundances in the Sun and 10 Metal-poor Stars
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改进了太阳和 10 颗贫金属恒星中 Hf II 和铪丰度的实验室跃迁概率
DOI：
10.1086/510368
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
I. Ivans
中科院分区：
文献类型：
--
作者：
J. Lawler;E. A. Hartog;Z. Labby;C. Sneden;J. Cowan;I. Ivans
激光诱导荧光测量的辐射寿命，精确到± 5%，报告了41奇宇称水平的铪II。结合使用傅里叶变换光谱测量的分支分数的寿命，以确定150线的Hf II的跃迁概率。这些新的跃迁概率中大约有一半与最近使用类似方法进行的独立测量重叠。发现两组测量结果对于共同的线非常一致。我们新的实验室数据被应用于改进的铪光球太阳丰度，并确定铪丰度在10个贫金属巨星增强r-过程丰度。对于太阳，我们从四条谱线得出log ε（Hf）= 0.88 ± 0.08;不确定性主要是由谱线的弱点及其与其他光谱特征的混合所决定的。在不确定度范围内，富r过程星具有恒定的Hf/La和Hf/Eu丰度比，log ε（Hf/La）= -0.13 ± 0.02（σ = 0.06）和log ε（Hf/Eu）= +0.04 ± 0.02（σ = 0.06）。观察到的Hf/Eu和La/Eu的平均恒星丰度比大于以前估计的太阳系r-过程的唯一值，这表明从r-过程的生产铪和镧的贡献有点大。新测定的Hf值可以作为计时器对的一部分，Th/Hf，以确定放射性恒星的年龄。
Radiative lifetimes from laser-induced fluorescence measurements, accurate to ~±5%, are reported for 41 odd-parity levels of Hf II. The lifetimes are combined with branching fractions measured using Fourier transform spectrometry to determine transition probabilities for 150 lines of Hf II. Approximately half of these new transition probabilities overlap with recent independent measurements using a similar approach. The two sets of measurements are found to be in good agreement for lines in common. Our new laboratory data are applied to refine the hafnium photospheric solar abundance and to determine hafnium abundances in 10 metal-poor giant stars with enhanced r-process abundances. For the Sun we derive log ε(Hf) = 0.88 ± 0.08 from four lines; the uncertainty is dominated by the weakness of the lines and their blending by other spectral features. Within the uncertainties of our analysis, the r-process-rich stars possess constant Hf/La and Hf/Eu abundance ratios, log ε(Hf/La) = -0.13 ± 0.02(σ = 0.06) and log ε(Hf/Eu) = +0.04 ± 0.02 (σ = 0.06). The observed average stellar abundance ratio of Hf/Eu and La/Eu is larger than previous estimates of the solar system r-process-only value, suggesting a somewhat larger contribution from the r-process to the production of Hf and La. The newly determined Hf values could be employed as part of the chronometer pair, Th/Hf, to determine radioactive stellar ages.