Accurate Atomic Transition Probabilities for Optical Lines of Fe-group Ions

早期的宇宙几乎完全由氢和氦组成。 恒星通过一系列被称为“核合成”的过程来积累行星所需的较重的化学元素，并最终形成生命。 最早的恒星可能与今天的恒星大不相同。 这些古老的恒星被称为“贫金属”恒星，因为它们的重元素丰度很低，是由最早的恒星的残余物形成的。贫金属恒星中的元素丰度可以作为我们银河系的“化石记录”，并可以帮助我们了解核合成的起源。测试早期宇宙的理论需要非常精确地测量贫金属恒星中的元素丰度。 要准确和精确地测定某一元素的丰度，首先需要在我们的实验室中准确测量该元素的原子跃迁性质。 该项目的目标是改进现有的元素原子数据，并利用这些数据来确定贫金属恒星的高精度丰度。 这项工作也可能带来有益于其他应用科学领域的改进，如照明和分析化学。研究生和本科生的培训和指导一直是，并将继续是这一计划的重要组成部分。 威斯康星州大学（UW）计划使用涉及激光，强大的光谱仪，同步辐射和其他现代方法的技术来测量急需的原子数据。近年来，华盛顿大学研制了一台3米阶梯光栅光谱仪，用于测量铁族物质在紫外线中的极弱谱线。 与通常用于此类测量的傅里叶变换光谱仪不同，3米中阶梯光栅光谱仪没有重要的（多路）噪声源。 这些弱谱线是恒星光球中丰度研究所需要的，因为丰富的铁族元素的强谱线是部分到深度饱和的，因此不是很好的丰度指标。 拟议的研究将扩大范围的3米阶梯光谱仪到光学应用在地基天文学。 该项目的第一阶段将涉及开发和实施仪器的辐射校准到硅探测器的极限接近10000埃。 然后，该仪器将用于测量Fe、Co和Ni离子光谱中具有天体物理学意义的弱光学线。 这些新的跃迁概率将被应用于确定太阳和贫金属恒星的准确和精确的丰度。

The early Universe was almost completely made up of hydrogen and helium. Stars build up the heavier chemical elements needed for planets and eventually for life through a series of processes known as "nucleosynthesis". The earliest stars were likely quite different than stars today. These old stars, called "metal-poor" stars because of their low abundance of heavier elements, were formed from the remnants of the earliest stars. Elemental abundances in metal-poor stars serve as a "fossil record" of our Galaxy and can help us understand the beginnings of nucleosynthesis. Testing theories of the early Universe requires very accurate measurements of elemental abundances in metal-poor stars. An accurate and precise abundance determination for a given element requires, first and foremost, accurate measurements in our laboratories of the atomic transition properties for that element. The goal of this project is to improve the available atomic data for elements and to use these data to determine highly accurate abundances in metal-poor stars. This work could also lead to improvements that benefit other fields of applied science, such as lighting and analytical chemistry. Training and mentoring of graduate students and of undergraduates has been, and will continue to be, an important part of this program. The University of Wisconsin (UW) program uses techniques involving lasers, powerful spectrometers, synchrotron radiation, and other modern approaches to measure critically needed atomic data. In recent years, a 3-meter echelle spectrometer was developed at UW to measure very weak lines of Fe-group species in the ultraviolet. Unlike Fourier transform spectrometers, which are often used for such measurements, the 3m echelle spectrometer is free from an important (multiplex) noise source. These weak lines are needed for abundance studies in stellar photospheres, because stronger lines of the abundant Fe-group elements are partially to deeply saturated and are therefore not good abundance indicators. The proposed research will extend the range of the 3m echelle spectrometer into the optical for applications in ground-based astronomy. The first phase of the project will involve developing and implementing a radiometric calibration for the instrument out to the Si detector limit near 10000 Angstroms. The instrument will then be used for the measurement of weak optical lines of astrophysical interest in the spectra of ions of Fe, Co, and Ni. These new transition probabilities will be applied to determine accurate and precise abundances in the Sun and in metal-poor stars.