Quantum State Resolved Studies of Gas-Surface Interaction Dynamics

在化学系物理化学计划的这个项目中，德克萨斯大学奥斯汀分校化学系的格雷格·O·西茨教授将进行一系列气体表面散射实验。基于分子束和激光的状态制备和检测技术的组合将被用来进行气体-表面相互作用动力学的完全量子态分辨研究。将研究分子氢和氢在单晶铜表面的散射和离解，以确定平移、转动、振动和分子排列在破坏散射事件结果方面的相对重要性。受激拉曼散射将被用来制备以第一激发振动态的选定旋转态入射到铜表面的氢分子。通过多光子电离，散射分子将以量子态特有的方式被探测到。分子与固体表面的初始接触可能会导致几种可能的结果，这取决于分子、表面以及在许多可用自由度之间的能量分配。这些可能性包括非弹性散射、陷阱、粘连和键断裂。在最后一种情况下，分子中的一个键可以被打破，通过在表面形成一个或多个化学键来付出能源代价。这是许多表面能够促进或参与化学反应的本质。然而，在许多令人感兴趣的情况下，即使反应在能量上是有利的，反应的概率也很低，因为存在障碍：据说反应是被激活的。人们最关心的是这种激活障碍的性质以及跨越它的动力机制。这项研究集中在解离吸附是一个活化过程的系统中的气体-表面相互作用。通过用全状态分辨测量进行这项研究，将获得对表面动力学的新见解，并将严格检验现有理论。

In this project in the PhysicalChemistry program of the Chemistry Division, Professor Greg O. Sitz of the Chemistry Department of the University of Texas at Austin will perform a series of gas-surface scattering experiments. A combination of molecular beam and laser based state preparation and detection techniques will be used to performm fully quantum state resolved studies of gas-surface interaction dynamics. The scattering and dissociation of molecular hydrogen and deuterium from single crystal copper surfaces will be studied to determine the relative importance of translational, rotational, vibrational and molecular alignment in dermining the outcome of the scattering event. Stimulated Raman scattering will be used to prepare hydrogen molecules incident on the copper surface in a selected rotational state of the first excited vibrational state. Scattered molecules will be detected in a quantum state specific manner by multiphoton ionization. The initial encounter of a molecule with a solid surface can lead to several possible results depending on the molecule , the surface, and the energy partitioning amongst the many available degrees of freedom. These possibilities include inelastic scattering, trapping, sticking and bond breaking. In the last case, a bond in the molecule can be broken, paying the energy price by forming one or more chemical bonds to the surface. This is the essence of the ability of many surfaces to promote or participate in chemical reactions. In many cases of interest, however, even though the reaction is energetically favorable, the reaction probability is low because of the presence of a barrier: the reaction is said to be activated. Of central concern is the nature of this activation barrier and the dynamical mechanism for crossing it. This research focuses on gas-surface interactions in systems where dissociative adsorption is an activated process. By performing this research with fully state resolved measurements new insight into surface dynamics will be gained and existing theories will be stringently tested.