Laboratory Studies Required to Understand Cometary Emissions: O(1S) and O(1D) Yields from CO2 Photodissociation in the Extreme Ultraviolet

了解彗星发射所需的实验室研究：极紫外光中 CO2 光解离产生的 O(1S) 和 O(1D) 产量

• 批准号: 1410297
• 负责人: Konstantinos Kalogerakis
• 金额: $ 36.6万
• 依托单位: SRI International
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-15 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1410297&HistoricalAwards=false
• 关键词: Laboratory; Studies; Required; Understand; Cometary

This award's main goal is to produce laboratory measurements that are needed to reliably interpret and quantify carbon dioxide emissions from comets. Comets are relatively small bodies made of ice and dirt that orbit the Sun; however, they spend most of their time very far from the Sun at very cold temperatures. Thus, they are considered to be among the best preserved and most primordial objects in the solar system and their chemical composition is key to constraining solar system formation models. Carbon dioxide is of particular interest because the molecule may be present in comet nuclei in high enough quantities that sublimation (going directly from ice to gas upon heating without ever becoming liquid water) may drive a significant portion of the activity as comets orbit close to the Sun. The PI and his research team will conduct experiments in order to better understand how carbon dioxide degrades in sunlight after sublimating from comet nuclei that are close to the Sun. The project focuses on two atomic oxygen emission lines commonly observed in comet spectra, which are possibly largely formed during the breakup of carbon dioxide. Since carbon dioxide is unobservable from ground-based telescopes, the atomic oxygen emission lines serve as a valuable proxy for carbon dioxide. This work will also be useful for modeling atmospheres of Mars, Venus and some exoplanets. The PI will train and mentor a postdoctoral fellow and summer undergraduate students in this research. The planned experiments will be carried out at the Advanced Light Source of the Lawrence Berkeley National Laboratory. The team will use synchrotron radiation to determine O(1S) and O(1D) yields from carbon dioxide photodissociation at 90-115 nm. In order to amplify detection of these two atomic states, which normally have long radiative lifetimes, they will introduce xenon gas to the samples, which enhances the radiative rate by a factor of 75. Knowledge of these excited atomic oxygen lines from carbon dioxide photodissociation will enable the use of the atomic oxygen red and green line emissions (at 630/636.4 nm and 557.7 nm, respectively) as a probe of cometary composition.

该奖项的主要目标是产生可靠地解释和量化彗星二氧化碳排放所需的实验室测量结果。彗星是由冰和尘埃组成的相对较小的天体，绕太阳运行;然而，它们大部分时间都在非常寒冷的温度下远离太阳。因此，它们被认为是太阳系中保存最完好和最原始的天体之一，它们的化学成分是限制太阳系形成模型的关键。 二氧化碳是特别令人感兴趣的，因为该分子可能以足够高的量存在于彗星核中，以至于升华（在加热时直接从冰变成气体而不会变成液态水）可能会在彗星靠近太阳的轨道上驱动相当大一部分活动。 PI和他的研究团队将进行实验，以更好地了解二氧化碳从靠近太阳的彗星核升华后如何在阳光下降解。 该项目的重点是在彗星光谱中经常观察到的两条原子氧发射线，这两条线可能主要是在二氧化碳分解过程中形成的。 由于地面望远镜无法观测到二氧化碳，因此原子氧发射谱线是二氧化碳的一个有价值的替代物。这项工作也将有助于模拟火星，金星和一些系外行星的大气。 PI将在这项研究中培训和指导博士后研究员和暑期本科生。计划的实验将在劳伦斯伯克利国家实验室的先进光源处进行。 该团队将使用同步辐射来确定O（1 S）和O（1D）在90-115 nm处的二氧化碳光解产率。 为了放大这两种原子状态的检测，它们通常具有较长的辐射寿命，他们将向样品中引入氙气，这将辐射率提高了75倍。 这些激发的原子氧线从二氧化碳光解的知识将使使用原子氧的红色和绿色线的排放（在630/636.4 nm和557.7 nm，分别）作为彗星组成的探针。