Laboratory Astrophysics: new atomic and molecular data for astrophysics applications

摘要：本研究是一个实验室研究项目，旨在为天体物理学应用提供新的精确的原子和分子数据。帝国理工学院实验室光谱学小组在使用我们的高分辨率傅立叶变换光谱仪以及通过国际合作进行高分辨率光谱研究方面有着悠久的历史。在许多情况下，对天体物理对象的研究涉及光谱分析，这需要一个原子和分子数据库来进行可靠的解释。地面和天基望远镜上的新型高分辨率光谱仪使天文学家能够观测到质量空前的天体物理光谱，并且迫切需要足够精确和完整的原子数据来分析这些光谱。尤其重要的是铁族元素（Ti， V, Cr, Mn, Fe, Co, Ni）丰富的谱线。虽然近年来原子数据有了很大的改进，但仍有一些关键的数据缺失，这些数据不完整或不准确，在中性和单电离物质的红外光谱中，往往完全缺失。利用我们在帝国理工学院的独特的可见-紫外傅立叶变换光谱仪和NIST（美国国家标准与技术研究所）和隆德大学（瑞典）的红外-可见傅立叶变换光谱仪，我们将研究这些元素的高分辨率光谱。使用傅立叶变换光谱仪的优点是我们可以在宽光谱范围内以高分辨率测量特定物种的光谱。我们将专注于在波长精度、原子能级、振荡器强度（用于确定天体物理对象中元素丰度）和超精细结构方面至少取得数量级改进的测量。天文学家利用这些原子数据来分析天体物理光谱。一旦测量到原子数据，将立即用于我们正在合作的特定天体物理学项目，例如：太阳光球层和低金属丰度恒星的化学成分，银河系化学演化的研究，低质量恒星，褐矮星和太阳系外行星，热恒星和化学特殊恒星。除了原子数据测量项目外，我们还计划一个新的双原子硫高分辨率分子光谱项目，该项目涉及紫外光谱测量，以获得各种研究迫切需要的分子数据，包括：木星卫星Io的大气和火山羽流；木星的大气层和彗星。我们所产生的所有新的实验室原子和分子数据都被纳入数据库和模型大气代码，除了英国的天文学家外，还使全世界的天文学家受益。我们向天文学界提供的新的实验室数据意味着，对昂贵获得的现代天体物理光谱的分析将不再受到分析中使用的原子（或分子）数据的质量和数量的限制。

Summary: This research is a programme of laboratory studies to give new accurate atomic and molecular data for astrophysics applications. The Imperial College laboratory spectroscopy group has a long history of high resolution spectroscopic studies using our high resolution Fourier transform spectrometers, and also through international collaborations. Studies of astrophysical objects in many cases involve analyses of spectra which require an atomic and molecular data base for their reliable interpretation. New high resolution spectrographs on both ground and space-based telescopes have allowed astronomers to observe astrophysical spectra of unprecedented quality, and have led to an urgent need for atomic data of sufficient accuracy and completeness to analyse these spectra. Particularly important are the abundant, line rich spectra of the iron group elements (Ti, V, Cr, Mn, Fe, Co, Ni). Although there has been great improvement in the atomic data in recent years, there remain key missing data, that are incomplete or inaccurate, and in the case of the infra red spectra of neutral and singly ionised species are often missing entirely. Using our unique visible-ultraviolet Fourier Transform (FT) spectrometer at Imperial College and the infrared-visible FT spectrometers at NIST (National Institute Standards & Technology, USA) and Lund University (Sweden) we will study high resolution spectra of these elements. The advantages of using an FT spectrometer are that we can measure the spectrum of a particular species at high resolution over a wide spectral range. We will focus on measurements leading to at least order-of-magnitude improvements in wavelength accuracy, atomic energy levels, oscillator strengths (needed for determining abundances of elements in astrophysical objects), and hyperfine structure. Astronomers use these atomic data in analysing astrophysical spectra. Once measured the atomic data will be used immediately in specific astrophysics projects we are collaborating on, examples include: chemical composition of the solar photosphere and low metallicity stars, studies of Galactic chemical evolution, low mass stars, brown dwarfs and extra solar planets, hot stars, and chemically peculiar stars. In addition to the program of atomic data measurements, we plan a new project of high resolution molecular spectroscopy of diatomic sulphur, which involves spectroscopic measurements in the ultraviolet, to yield molecular data urgently needed for a variety of studies including: atmosphere and volcanic plumes of Io, a moon of Jupiter; the atmosphere of Jupiter, and cometary comae. All the new laboratory atomic and molecular data we produce is incorporated into databases and model atmosphere codes, benefiting astronomers worldwide in addition to those in the UK. The new laboratory data we provide to the astronomical community means that analyses of expensively obtained modern astrophysical spectra will no longer be limited by the quality and quantity of atomic (or molecular) data used in their analyses.