Laboratory Astrophysics of Interstellar Ice Mantles

奖项：AST-0807832发起人：弗吉尼亚大学主校区：劳尔·A·巴拉吉奥拉：星际冰盖的实验室天体物理学这项研究将解决暗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中心问题之一。问题包括：由于分子云的温度低和凝聚系数高，所有气体物种，除了H2和He，都会在通常10万年的时间里被颗粒上的凝结耗尽。然而，典型的分子云寿命要长得多，有数百万年之久，并且在气相中含有相对较高数量的分子。因此，一个高效的解吸机制必须运转起来。然而，所有拟议的机制都不能令人信服地维持所观察到的气体数量。为此，将在这里进行的实验室研究进行了新的实验来确定脱附速率，其原因是：a)由紫外线Lyman-α光子进行的光解吸，b)通过H原子与吸附在冰上的H2分子的重新组合而产生的热脱附，c)由低能电子引起的解吸。此外，由于分子云中的主要星际气体是分子氢，分子氢很容易被微孔水冰吸收，所以实验将模拟这些条件，研究氢的吸附，通过吸附其他气体如CO来取代氢，以及吸附的氢对水冰中的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力和质谱分析技术来测量超高真空低温下冰块的解吸。该研究小组展示了该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问题来促进创新，例如，分子云中将出现低能电子解吸的新概念。除了研究的天文应用外，这里开发的对材料辐射处理的理解在半导体、薄膜和化学工业中也有应用。巴拉吉奥拉博士正在与科学家合作研究其中的一些应用。学生将是这项研究的积极参与者，该研究将为学生提供培训，为他们在工业、政府和学术职业生涯中做好准备。一些研究还将被纳入本科天文学入门课程，部分原因是为了帮助学生理解实验室天体物理学在我们正在进行的理解宇宙的探索中所起的作用。

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.