Sputtering, Radiolysis, and Photolysis: Physical Mechanisms and Astrophysical Applications

溅射、辐射分解和光解：物理机制和天体物理应用

• 批准号: 0507030
• 负责人: Robert Johnson
• 金额: --
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2009-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0507030&HistoricalAwards=false
• 关键词: Sputtering; Radiolysis; Photolysis; Physical; Mechanisms

AST 0507030JohnsonEnergetic charged particles, UV photons and x-rays alter materials in a number of astrophysical environments. Such radiations can change the composition of ices and other low temperature molecular solids and cause the ejection of atoms and molecules. Therefore, the chemistry induced in materials by photons, called photolysis, and that produced by charged particles, called radiolysis, are related to the production of gas-phase species, typically called desorption or sputtering. UV-photons, x-rays and cosmic-ray (CR) ions maintain the gas-phase species observed in regions of the interstellar medium (ISM), in discs around young stellar objects (YSOs) and in the recently discovered oxygen atmosphere over Saturn's rings. A giant toroidal atmosphere is produced in Saturn's inner magnetosphere by sputtering of grains. Europa and Ganymede have chemically altered surfaces and gravitationally bound oxygen atmospheres produced by energetic ions and electrons. The possible presence of a sub-surface ocean on Europa has lent importance to obtaining a description of the radiolytic production of oxidants in its relatively young surface. In order to understand these exciting observations, it is necessary to develop models of sputtering, radiolysis, and photolysis that can be used by astronomers. Because the surfaces and ambient gases are coupled by radiation processing, practical models will be constructed using the latest computational tools in materials science as guides. With such models, gas or plasma observations in an astrophysical environment can be used to determine the composition of embedded surface materials. Conversely, observations of the composition of the surface materials can be used to predict the ambient neutral and plasma environments. Although the commonality of the physical and chemical processes occurring in a number of space environments is the focus of this research, the models will be applied to the surface-plasma coupling in Saturn's magnetosphere, to the irradiation of the surface of Europa, and to x-ray-induced production of gas from the discs of YSOs. The fundamental physics and chemistry of radiation processing of molecular solids will be described. Because a massive amount of data is needed for a broad range of materials and radiation types (x-rays, CR ions, solar and magnetopheric plasmas), a research program is needed that summarizes the available data, then uses the modern computational tools in materials science to develop applicable models, and finally applies the new models to a number of topical problems.This work integrates problems in astronomy with those in material science. Because of the emphasis on underlying physics and chemistry, the models that are developed are of interest to a broad scientific community. In fact, this research, which is driven by the need to understand astrophysical observations, has already had an impact on the physics and chemistry of radiation modification of molecular materials and has altered the teaching of introductory materials courses. Because of its interdisciplinary nature, the research will be carried out by students in Engineering Physics at the University of Virginia. This is a model cross-disciplinary graduate program that has strong interactions with neighboring undergraduate institutions and high schools that serve primarily minority populations. ***

AST 0507030JohnSonEnergetic带电颗粒，紫外光子和X射线改变了许多天体物理环境中的材料。这样的辐射可以改变IC和其他低温分子固体的组成，并引起原子和分子的弹出。因此，通过光子（称为光解的材料）诱导的化学反应，而被带电颗粒（称为辐射溶解）产生的化学与气相物种的产生有关，该物种的产生通常称为解吸或溅射。 紫外线，X射线和宇宙射线（CR）离子维持在星际介质（ISM）的区域中观察到的气相物种，在年轻恒星物体（YSOS）周围的碟片以及最近在土星环上发现的氧气大气。通过晶粒的溅射，在土星的内部磁层中产生了巨大的环形气氛。欧罗巴和甘植物具有化学改变的表面，并由能量离子和电子产生的重力结合的氧气大气。欧罗巴上的地下海洋的可能存在对于获得相对年轻的表面上氧化剂的放射性氧化剂的描述非常重要。 为了理解这些令人兴奋的观察结果，有必要开发天文学家可以使用的溅射，放射分解和光解的模型。 由于表面和环境气体与辐射处理相结合，因此将使用材料科学中最新的计算工具作为指南来构建实用模型。 使用此类模型，可以使用天体物理环境中的气体或血浆观测来确定嵌入式表面材料的组成。相反，对表面材料组成的观察可用于预测环境中性和血浆环境。尽管在许多空间环境中发生的物理和化学过程的共同点是这项研究的重点，但这些模型将应用于土星磁层中的表面 - 气皮耦合，欧罗巴表面的照射，以及X射线诱导的YSOS唱片的气体产生。将描述分子固体的辐射加工的基本物理和化学。由于需要大量数据（X射线，CR离子，太阳能和磁性等离子体）需要大量数据，因此需要进行一项研究程序来汇总可用数据，然后使用材料科学中的现代计算工具来开发适用的模型，并最终将新模型应用于与天文学的许多材料中的许多问题。 由于强调潜在的物理和化学，因此开发的模型吸引了广泛的科学界。实际上，这项由了解天体物理学观察的需要驱动的这项研究已经对分子材料的辐射修饰的物理和化学产生了影响，并改变了入门材料课程的教学。由于其跨学科的性质，该研究将由弗吉尼亚大学的工程物理学学生进行。这是一个跨学科的模型研究生课程，与邻近的本科机构和主要服务于少数民族人口的高中有牢固的互动。 ***