Absorption of Radiation by Hot, Dense Mixtures of Hydrogen and Helium

氢和氦的热致密混合物吸收辐射

• 批准号: 0708496
• 负责人: Katharine Hunt
• 金额: $ 16.17万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0708496&HistoricalAwards=false
• 关键词: Absorption; Radiation; Hot; Dense; Mixtures

This project is motivated by the inadequacy of existing calculations of collision-induced absorption involving H2 molecules in very cool white dwarfs. These stars are the remains of the earliest generation of stars in our Galaxy and form the basis for a method to determine the age of this stellar population. Knowledge of collision-induced absorption spectra at high densities, high temperatures and frequencies is crucial for the determination of atmospheric compositions, effective temperatures, cooling rates, and cooling ages.Here, opacities arising from collision induced absorption in dense hydrogen gas and hydrogen-helium mixtures at temperatures from 1000 to 6000 K and frequencies up to 25,000 inverse centimeters will be calculated from first principles. These collision-induced absorption coefficients will be obtained by direct integration of the Schrödinger equation of the H2-X scattering process in the presence of photons, with X = H2, He, and/or H. Besides the binary absorption coefficients, estimates of the ternary absorption of both the pairwise-additive components and the strongest long-range, irreducible components will be obtained. The contribution of ternary complexes such as H2-H2-H2, H2-He-He, and He-He-He, presently unaccounted for but known to be important will also be evaluated and made available through this work. Through collaboration with Dr. Didier Saumon (Los Alamos National Laboratory) and the Stellar Atmospheres Group at the University of Texas, headed by Dr. Don Winget, these new collision-induced absorption calculations will find immediate applications in the modeling of the atmospheres of very cool white dwarf stars.Several peculiar white dwarfs currently defy interpretation with current models and it is hoped that the work to be carried out here will shed light on these problems. It is further expected that the analysis capabilities enabled by the new collision-induced opacities will have immediate application in a number of other fields, such as Galactic astronomy and stellar evolution. Two graduate students will be supported through this project and trained in implementing algorithms for numerical solutions, intensive numerical computations, programming, and testing.

这个项目的动机是现有的计算的不足碰撞诱导吸收涉及氢分子在非常冷的白色矮星。这些恒星是我们银河系中最早一代恒星的遗骸，并形成了确定这一恒星群年龄的方法的基础。在高密度、高温度和高频率下的碰撞诱导吸收光谱的知识对于确定大气成分、有效温度、冷却速率和冷却年龄是至关重要的。这里，在1000至6000 K的温度和高达25 ° C的频率下，000厘米的倒数将根据第一原理计算。这些碰撞诱导吸收系数将通过在光子存在下H2-X散射过程的薛定谔方程的直接积分获得，其中X = H2，He和/或H。除了二进制吸收系数，估计的三元吸收的两个成对的添加剂成分和最强的长程，不可约的组件将获得。三元复合物，如H2-H2-H2，H2-He-He，和He-He-He，目前尚不清楚，但已知是重要的贡献也将通过这项工作进行评估和提供。通过与Didier Saumon博士的合作（洛斯阿拉莫斯国家实验室）和得克萨斯大学的恒星大气组，由唐·温盖特博士领导，这些新的碰撞-诱导吸收的计算将在非常冷的白色矮星的大气模型中找到直接的应用。目前，一些特殊的白色矮星无法用现有的模型解释，希望在这里进行的工作将为这些问题提供线索。人们还预计，新的碰撞引起的不透明度所带来的分析能力将立即应用于其他一些领域，如银河系天文学和恒星演化。两名研究生将通过该项目得到支持，并接受实施数值解算法、密集数值计算、编程和测试方面的培训。