Er II实验室跃迁几率的改进及其在太阳和五颗富r过程贫金属恒星铒丰度研究中的应用
Improved Laboratory Transition Probabilities for Er II and Applications to the Erbium Abundances of the Sun and Five r-Process Rich, Metal-Poor Stars
摘要：
最近使用激光诱导荧光（LIF）对Er II的8个偶宇称和62个奇宇称能级进行的精确到+/-5%的辐射寿命测量（Stockett等人，2007，J. Phys. B 40，4529）已经与使用傅里叶变换光谱仪（FTS）测量的新的分支分数相结合，以确定Er II的418条线的跃迁概率。这项工作将Er II移动到不断增长的稀土光谱列表中，并使用LIF加FTS数据进行了广泛而准确的现代跃迁概率测量。这个改进的实验室数据集已被用来确定一个新的太阳光球Er丰度，log γ = 0.96 +/- 0.03（8条线的σ = 0.06），一个非常符合推荐的流星体丰度，log γ = 0.95 +/- 0.03的值。修正后的Er丰度也被推导出了富含r-过程的贫金属巨星CS 22892-052、BD+17 3248、HD 221170、HD 115444和CS 31082-001。这五颗恒星的平均Er/Eu丰度比<log Eu（Er/Eu）> = 0.42，与太阳系r过程比非常吻合。这项研究进一步加强了这一发现，即在早期银河系中富集这些贫金属恒星的r-过程核合成产生了与富集包括太阳在内的后来恒星的r-过程非常相似的模式。
英文摘要：
Recent radiative lifetime measurements accurate to +/- 5% (Stockett et al. 2007, J. Phys. B 40, 4529) using laser-induced fluorescence (LIF) on 8 even-parity and 62 odd-parity levels of Er II have been combined with new branching fractions measured using a Fourier transform spectrometer (FTS) to determine transition probabilities for 418 lines of Er II. This work moves Er II onto the growing list of rare earth spectra with extensive and accurate modern transition probability measurements using LIF plus FTS data. This improved laboratory data set has been used to determine a new solar photospheric Er abundance, log epsilon = 0.96 +/- 0.03 (sigma = 0.06 from 8 lines), a value in excellent agreement with the recommended meteoric abundance, log epsilon = 0.95 +/- 0.03. Revised Er abundances have also been derived for the r-process-rich metal-poor giant stars CS 22892-052, BD+17 3248, HD 221170, HD 115444, and CS 31082-001. For these five stars the average Er/Eu abundance ratio, <log epsilon (Er/Eu)> = 0.42, is in very good agreement with the solar-system r-process ratio. This study has further strengthened the finding that r-process nucleosynthesis in the early Galaxy which enriched these metal-poor stars yielded a very similar pattern to the r-process which enriched later stars including the Sun.
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