Irradiation of Low Temperature Solids: Physical Mechanisms and Astrophysical Implications

低温固体辐照：物理机制和天体物理意义

• 批准号: 0098523
• 负责人: Robert Johnson
• 金额: $ 14.63万
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-01 至 2005-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0098523&HistoricalAwards=false
• 关键词: Irradiation; Low; Temperature; Solids; Physical

AST 0098523JohnsonDr. Robert Johnson, at the University of Virginia, will continue a research program to model the radiolysis and photolysis of low temperature solids in the outer Solar System and the interstellar medium (ISM). Irradiation by charged-particles or UV-photons of ice, molecules trapped in an ice matrix or hydrated minerals can determine the ambient neutral envelopes and the spectral properties of outer solar system satellites and of grains in the ISM. An understanding of the interaction of energetic ions, electrons and UV -photons with surfaces is needed to interpret many recent observations .A large body of laboratory data now exists on the sputtering and decomposition of low temperature condensed-gas solids. This data set has some inconsistencies, as well as large gaps in the materials studied and in the incident particle type and energies studied. It has only recently been shown that the long-ignored energetic electrons are important when describing the alteration of icy satellite surfaces. Therefore, Dr. Johnson will carry out a materials-based calculation program to model the available data and then use the results to expand the applicability of these data. His recent molecular dynamics calculations of energy transport during the sputtering of ices will be used to describe the sputtering of volatile and refractory species trapped in an ice matrix. In addition, he will incorporate and test those solid-state chemistry models that have been proposed for the production and desorption of new molecules due to irradiation of ice. The goal is to be able to calculate results for all charged particle types and energies, including cluster impact, for application to sputtering of a grain in the ISM, a ring particle, or a satellite regolith with a grain size and porosity much different than that used in laboratory studies. Such work is possible due to the rapid improvements in the computational tools available in materials science and because there exists an extensive set of data that can be used to test and calibrate these methods for the materials of interest in the outer Solar System and the ISM . Monte Carlo (MC) particle transport codes, which determine the distribution of energy deposition in a material, will be used along with molecular dynamics (MD) models and a continuum model to describe the energy transport and sputtering. The suggested chemical pathways for radiolysis and photolysis will be integrated in the MD model in order to describe aspects of the radiation-induced solid-state chemistry occurring in ice. Finally, Dr. Johnson will continue to assemble laboratory data from the large number of groups studying ion, electron and photon-induced sputtering and implantation and then incorporate these data into the proposed calculations .***

AST 0098523Johnsondr。弗吉尼亚大学的罗伯特·约翰逊（Robert Johnson）将继续一项研究计划，以对外太阳系和星际培养基（ISM）中低温固体的放射分解和光解建模。 被带电粒子或冰片，冰基中的分子或水合矿物质的分子辐射可以确定环境中性信封以及ISM中外太阳系卫星和晶粒的光谱特性。 需要理解能量离子，电子和紫外线与表面的相互作用，以解释许多最近的观察结果。现在存在大量的实验室数据，这是关于低温冷凝 - 气体固体的溅射和分解。该数据集在研究的材料以及所研究的入射粒子类型和能量中存在一些不一致之处，以及大量的差距。 直到最近才表明，在描述冰冷卫星表面的变化时，长期签名的能量电子很重要。因此，约翰逊博士将执行基于材料的计算程序，以建模可用数据，然后使用结果扩展这些数据的适用性。他最近在溅射IC的能量传输的分子动力学计算将用于描述被困在冰基质中的挥发性和难治物种的溅射。此外，他将合并并测试那些因冰辐射而提出的用于生产和解吸新分子的固态化学模型。目的是能够计算所有带电的颗粒类型和能量（包括簇撞击）的结果，以应用于在ISM中溅射谷物，环粒子或卫星岩石石材，其晶粒尺寸和孔隙率与实验室研究中使用的晶粒尺寸和孔隙率有很大不同。由于材料科学中可用的计算工具的快速改进，因此可以使用此类工作，并且由于存在大量数据，这些数据可用于测试和校准这些方法，以供外部太阳系和ISM中感兴趣的材料。 确定材料中能量沉积的分布的Monte Carlo（MC）粒子传输代码将与分子动力学（MD）模型一起使用，并使用连续模型来描述能量传输和溅射。建议的放射分解和光解的化学途径将集成在MD模型中，以描述冰中发生的辐射诱导的固态化学的各个方面。最后，约翰逊博士将继续从研究离子，电子和光子诱导的溅射和植入的大量小组中组装出实验室数据，然后将这些数据纳入拟议的计算中。***