Laboratory Astrophysics of Interstellar Ice Mantles

奖学金编号：AST - 0807832INSTITUTION: University of Virginia Main校区pi: Raul A baragiolati标题：星际冰幔的天体物理学实验室这项研究将解决暗物质星际分子云中气体分子和尘埃颗粒之间的平衡问题，这是星际物质演化中尚未解决的核心问题之一。问题包括：由于分子云的低温和高冷凝系数，除了H2和He外，所有的气态物质都会在10万年的时间里通过颗粒的冷凝而耗尽。然而，典型的分子云存在的时间要长得多，有数百万年，并且含有相对较多的气相分子。因此，必须建立有效的解吸机制。然而，所提出的机制都不能令人信服地维持观测到的气体种群。由于这个原因，这里的实验室研究将进行新的实验，以确定由于：a)紫外莱曼- α光子的光解吸，b)氢原子重组成吸附在冰上的H2分子的热解吸，c)低能电子引起的解离电子附着的解吸。此外，由于分子云中的星际气体主要是分子氢，而分子氢在微孔水冰中很容易被吸收，因此实验将模拟这些条件，研究H2的吸附、CO等其他气体对H2的吸附，以及吸附氢对水冰中光解吸和分子光合作用的影响。这项研究将使用高度灵敏的微重和质谱技术来测量超低温下超高真空条件下冰的解吸。该研究小组展示了在研究领域的专业知识，并通过将其他科学领域的知识和技术应用于天文学问题来促进创新，例如低能电子解吸将发生在分子云中的新概念。除了天文应用的研究，这里开发的材料辐射加工的理解在半导体，薄膜和化学工业的应用。巴拉吉奥拉博士正在与科学家合作研究其中的一些应用。学生将积极参与这项研究，为学生提供培训，为他们在工业、政府和学术领域的职业道路做好准备。其中一些研究也将被纳入本科天文学入门课程，部分目的是帮助学生了解实验室天体物理学在我们不断探索宇宙的过程中所扮演的角色。

AWARD NO: AST - 0807832INSTITUTION: University of Virginia Main CampusPI: Raul A BaragiolaTITLE: Laboratory Astrophysics of Interstellar Ice MantlesThis research will address the question of the balance between molecules in the gas and on dust grains in dark interstellar molecular clouds, one of the central unsolved problems in the evolution of interstellar matter. The problem consists of the following: due to the low temperature of molecular clouds and high condensation coefficients, all gaseous species, with the exception of H2 and He would be depleted by condensation on grains, in times of typically 100,000 years. Yet a typical molecular cloud lives much longer, millions of years, and contains a relatively high number of molecules in the gas phase. Therefore, an efficient desorption mechanisms must operate. However, none of the proposed mechanisms can convincingly maintain the gas population observed. For this reason, the laboratory studies to be undertaken here perform novel experiments to determine desorption rates due to: a) photodesorption by ultraviolet Lyman-alpha photons, b) thermal desorption by recombination of H atoms into H2 molecules adsorbed on ices, c) desorption from dissociative electron attachment caused by low energy electrons. In addition, since the main interstellar gas in molecular clouds is molecular hydrogen, which can be readily absorbed in microporous water ice, the experiments will simulate those conditions, studying H2 adsorption, replacement of H2 by adsorption of other gases such as CO, and the effect of adsorbed hydrogen on the photodesorption and molecular photosynthesis in water ice. The research will use highly sensitive techniques of microgravimetry and mass spectrometry to measure desorption of ices at cryogenic temperatures in ultrahigh vacuum. The research group has demonstrated expertise in the research area and promote innovation by applying knowledge and techniques from other areas of science into astronomical problems, such as the new concept that desorption by low energy electrons will occur in molecular clouds. In addition to the astronomical applications of the research, the understanding of radiation processing of materials developed here has applications in semiconductor, thin film and chemical industries. The Dr. Baragiola is collaborating with scientists on some of these applications. Students will be active participants in this research which will provide training for students that will prepare them for industrial, government and academic career paths. Some of the research will also be incorporated into undergraduate introductory astronomy courses in part to help students understand the role laboratory astrophysics plays in our ongoing quest to understand our universe.