Atomic-level Imaging and Molecular Beam Scattering Studies of Interfacial Chemical Dynamics

在化学系化学结构，动力学和机制-A（CSDM-A）计划的支持下，芝加哥大学的Steven Sibener教授正在研究分子与表面碰撞时发生的化学反应。了解这些气体表面反应是具有挑战性的，因为反应的可能性取决于分子撞击表面的速度和角度，这些都很难控制。更复杂的是，当近距离观察表面时，它们表现出许多原子尺度的结构，包括台阶、缺失的原子和岛，每一种结构都可以表现出不同的反应性。Sibener教授和他的学生将使用分子束来控制与表面的碰撞，然后可视化分子如何附着，反应和离开界面。他们的发现可以揭示在许多新兴技术中控制化学反应的潜在机制，包括设计和开发用于可持续化学和量子信息科学应用的新功能材料。该项目还将通过为本科生、研究生和博士后学者提供研究机会，以及涉及当地学校和芝加哥科学与工业博物馆的外联活动，为国家科学、技术、工程和数学（STEM）劳动力的发展做出贡献。该项目将研究表面化学动力学中的问题，包括特定位置的反应性，绝热和非绝热气体-表面相互作用，如解离化学吸附，包括能量耗散和表面迁移率，定向控制沉积和薄膜生长，薄膜反应性，以及几何约束和立体特异性反应研究，其中高能原子物种与预-由于它们的键合和膜结构的性质而对准。反应物将使用定向表面吸附或自组装单层上的预定反应性端基进行预对准，从而向入射气相试剂呈现空间控制的反应伙伴。这将允许使用限定的入口通道反应条件系统地探索分子反应性和反应途径，所述限定的入口通道反应条件包括相对于分子骨架的明确限定的能量和极角/方位角攻角。与解离化学吸附和反应散射计算，结合量子理论和分子动力学模拟进行比较，将导致计算的反应势能面和机械反应途径的精度测试。控制试剂能量、入射角、强度和量子态将使非平衡能量条件下的界面化学检查成为可能。该奖项反映了NSF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。

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) program in the Division of Chemistry, Professor Steven Sibener of the University of Chicago is studying chemical reactions that occur when molecules collide with surfaces. Understanding these gas-surface reactions is challenging, since the likelihood of reaction depends on the speed and angle that molecules strike the surface, and these are difficult to control. Further complicating matters, when surfaces are viewed up close, they exhibit many atomic-scale structures, including steps, missing atoms, and islands, each of which can exhibit different reactivity. Professor Sibener and his students will use molecular beams to control the collision with the surface and then visualize how molecules attach to, react, and depart from the interface. Their discoveries could reveal the underlying mechanisms that govern chemical reactivity in a host of emerging technologies, including the design and development of new functional materials for sustainable chemistry and quantum information science applications. The project will also contribute to the development of the Nation's science, technology, engineering, and mathematics (STEM) workforce by providing research opportunities for undergraduate students, graduate students, and postdoctoral scholars, as well as outreach activities involving local schools and Chicago’s Museum of Science and Industry. This project will examine issues in surface chemical dynamics that include site specific reactivity, adiabatic and non-adiabatic gas-surface interactions such as dissociative chemisorption including energy dissipation and surface mobility, directionally-controlled deposition and film growth, thin film reactivity, and geometry-constrained and stereo-specific reaction studies in which energetic atomic species react with molecules that are pre-aligned due to the nature of their bonding and film structure. Reactants will be pre-aligned using either oriented surface adsorption or pre-ordered reactive end-groups on self-assembled monolayers, thus presenting sterically controlled reaction partners to incident gas phase reagents. This will allow systematic exploration of molecular reactivity and reaction pathways using defined entrance channel reaction conditions including well-defined energy and polar/azimuthal angles of attack with respect to the molecular framework. Comparisons with dissociative chemisorption and reactive scattering calculations, done in conjunction with quantum theory and molecular dynamics simulations, will lead to precision tests of calculated reaction potential energy surfaces and mechanistic reaction pathways. Control of reagent energy, incident angle, intensity, and quantum state will enable the examination of interfacial chemistry under non-equilibrium energetic conditions.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.