Investigation of the Formation of Water and of the Growth of Ices on Dust Grain Analogues

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该项目将在模拟星际介质和行星环境的条件下研究水分子的形成和冰的生长。众所周知，水是与生命的出现和可持续性相关的复杂化学反应的先决条件，然而，人们对水分子的实际形成方式知之甚少，尽管很明显，气相反应不足以解释在太空中观察到的丰富的水和水冰。这项具有挑战性的工作利用了该小组在低通量反应物、氢和氧原子束、质谱、原位红外光谱和表面表征探针等领域的专业知识和独特的实验室技术，并涉及与理论团队的密切合作。该项目将研究通过氢化反应和高能粒子相互作用在颗粒上形成水的机理和速率，测量冰幔形成早期颗粒的变化，确定冰的生长和光解作用，评价氢与O形成水、氢与H形成氢分子、氢与CO形成各种不同分子的竞争反应。该团队还将确定氘化率和途径。理论分析将使用实验确定的参数来获得空间环境条件下的反应速率。这项研究对于解释当前和未来地面和太空望远镜的结果具有广泛的价值，例如斯皮策和赫歇尔卫星以及阿塔卡马大型毫米波阵列。它将对水的形成和冰的形成提供前所未有的了解。预期的理论理解将使星际和行星化学的所有建模者受益。该项目为学生提供了一个在天体物理学、行星科学和表面科学研究前沿的跨学科领域工作的机会。特别是首席研究员非常积极地参与由地方和国家组织赞助的外展项目，并为本科生和高中生提供公认的培养环境。

AST-0908108VidaliThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This project will investigate the formation of water molecules and the growth of ice in conditions that simulate the interstellar medium and planetary environments. Water is a well-recognized prerequisite for the complex chemistry linked to the emergence and sustainability of life, and yet little is known of how water molecules actually form, although it is clear that gas-phase reactions are inadequate to explain the observed abundance of water and water-ice in space. This challenging work exploits the group's expertise and unique laboratory techniques in areas such low fluxes of reactants, hydrogen and oxygen atomic beams, mass spectrometry, in-situ infrared spectroscopy, and surface characterization probes, and involves close collaboration with a theoretical team. The program will study the mechanism and rates of water formation on grains via hydrogenation reactions and interaction with energetic particles, measure the alteration of grains early in ice-mantle formation, determine how ices grow and the effect of photo-dissociation, and evaluate the competing reactions of H with O to form water, H with H to form molecular hydrogen, and H with CO to form various different molecules. The team will also determine the deuteration rate and pathways. Theoretical analysis will use the experimentally determined parameters to obtain reaction rates in space environment conditions.This research is widely valuable for interpreting results from current and future ground- and space-based telescopes, such as the Spitzer and Herschel satellites and the Atacama Large Millimeter Array. It will provide an unprecedented understanding of the formation of water and the growth of ices. The anticipated theoretical understanding will benefit all modelers of interstellar and planetary chemistry. The project provides students with an opportunity to work in an interdisciplinary field at the forefront of research in astrophysics, planetary science and surface science. The principal investigator in particular is very active in outreach programs sponsored by local and national organizations and provides a recognized nurturing environment to undergraduate and high-school students.