Untangling the Energetics and Dynamics of Reactions of Ground State Silylidyne Radicals with Mononuclear Main Group Hydrides

在这个由化学部化学结构动力学和机理（CSDM-A）项目资助的项目中，夏威夷大学马诺阿分校的Ralf I. Kaiser教授正在探索含有一个硅和一个氢原子的简单分子（SiH，正式名称为“硅烷”）与其他分子(如水（H2O），硫化氢（H2S）和氨（NH3）之间的化学反应。简单碳分子与H2O、H2S和NH3之间的类似反应研究得很好，但对相应的硅反应知之甚少。碳和硅的化学性质在很多方面都很相似，甚至有些科学家提出了这样的问题：“为什么地球上的生命是以碳元素而不是硅元素为基础的？”凯泽教授的研究是探索含有硅和碳的分子的化学反应性的差异，并为一般的化学反应提供见解。这项研究也具有广泛的意义，并直接有助于天体化学家和天体生物学家正在进行的将太空化学与恒星的诞生、行星的形成和生命的进化联系起来的努力。更广泛地说，该项目通过传播其研究成果，通过跨学科专题讨论会向研究人员、大学生和高中教师开展外展活动，通过扩大未被充分代表的少数民族的参与，以及通过将项目的最新突破直接传达给教育工作者，使他们能够将研究活动纳入课堂课程，从而影响社会。通过与加州大学伯克利分校的Martin Head-Gordon教授合作，对基态水飞烷自由基（SiH）与原型单核主基（IV - VI）氢化物进行最先进的交叉分子束实验，并将这些结果与从头算和准经典轨迹（QCT）计算相结合，提出的研究探索了迄今为止难以捉摸的含硅体系的化学动力学，并解开了奇异的双核含硅分子的形成。其中许多只在理论上被预测存在。该项目正在推进对硅基分子化学键的基本理解，转变对化学活化含硅活性中间体的单分子分解的认识，并评估控制它们的过程，建立含硅分子系统中非绝热反应动力学的预测概念。并通过比较水飞蓟烷自由基（SiH）与同价甲基乙炔（CH）体系的反应动力学，阐明分子水平上的同价感知。参与的研究生和本科生将接受尖端实验室技术（反应散射实验、超高真空装置、激光技术）以及数据分析和在同行评审期刊上传播他们的研究成果的培训。PI小组还计划每年举办一个为期一周的全国暑期教师研讨会，针对本地和大陆高中的教师，强调天体化学的动手实验活动，以及如何将气相化学（反应机制、化学动力学）的基础研究结果应用于更好地理解太阳系（彗星、陨石、行星和卫星）和星际介质中发生的化学反应。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In this project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Professor Ralf I. Kaiser of the University of Hawaii at Manoa is exploring chemical reactions between a simple molecule containing one silicon and one hydrogen atom (SiH, formal name "silylidyne") with other molecules such as water (H2O), hydrogen sulfide (H2S) and ammonia (NH3). Similar reactions between simple carbon molecules and H2O, H2S and NH3 are well-studied, but little is known about the corresponding silicon reactions. The chemistry of carbon and silicon are similar in many ways, even to the point that some scientists have asked the question, "why is life on Earth based on the element carbon, and not silicon?" Professor Kaiser's research is exploring the differences in chemical reactivity of molecules containing silicon and carbon, and is providing insights into chemical reactions in general. This research is also broad implications and directly contributes to an ongoing effort by astrochemists and astrobiologists to connect the chemistry of space to the birth of stars, the formation of planets, and the evolution of life. More broadly, this project impacts society through the dissemination of its research results, through outreach activities to researchers, college students, and high school teachers via interdisciplinary symposia, by broadening the participation of underrepresented minorities, and by relaying the project's latest breakthroughs directly to educators enabling them to incorporate research activities into classroom curricula.By conducting state-of-the-art crossed molecular beam experiments of ground state silylidyne radicals (SiH) with prototype mononuclear main group (IV - VI) hydrides and combining these results with ab initio and quasi-classical trajectory (QCT) calculations in collaboration with Prof. Martin Head-Gordon (UC Berkeley), the proposed investigations explore the hitherto elusive chemical dynamics of silicon-bearing systems and untangle the formation of exotic dinuclear silicon-carrying molecules, of which many have only been predicted to exist theoretically. The project is advancing the fundamental understanding of the chemical bonding of silicon-based molecules, transform the knowledge of the unimolecular decomposition of chemically activated silicon-bearing reactive intermediates and evaluate the processes which control them, establish predictive concepts of non-adiabatic reaction dynamics in silicon-bearing molecular systems, and illuminate the perception of isovalency on the molecular level by comparing the reaction dynamics of the silylidyne radical (SiH) with those of the isovalent methylidyne (CH) systems. Participating graduate and undergraduate students are being trained in cutting-edge laboratory techniques (reactive scattering experiments, ultra-high vacuum setups, laser techniques) along with data analysis and dissemination of their research results in peer-reviewed journals. The PI's group also plans an annual one-week National Summer Teacher Workshop, aimed at teachers from local and mainland high schools, that emphasizes hands-on laboratory activities in astrochemistry and how the results from fundamental research in gas phase chemistry (reaction mechanisms, chemical dynamics) are applied to better understand the chemistry occurring in the solar system (comets, meteorites, planets and moons) and interstellar medium.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.