Ultraviolet Surface Photodynamics and Photochemistry

该项目涉及分析和表面化学的一般领域以及光化学和表面反应动力学的子领域。这项研究继续了首席研究员的光致碎裂研究，通过紫外激光激发的内部排斥状态，吸附在金属和半导体表面的分子。产生在表面反应中重要的自由基的光致碎裂可以在这些表面上进行，即使在存在通过能量转移到衬底的激发态的非常快（250 - 2500飞秒）的淬灭的情况下。将通过测量一系列小吸附物分子的截面、光碎片速度和角分布以及极化依赖性来研究更快的电荷转移过程（5 - 50 fs）的作用。紫外激光表面光化学是一个重要的新的基础研究领域，在半导体加工、太阳能转换、化学催化和眼科手术等领域有着广泛的应用前景。然而，人们对光化学反应的基本机制知之甚少。电荷转移和电子附着都被认为是重要的反应通道。吸附分子的光致碎裂研究将提供一个高度具体的探针的能量和电荷转移的动态界面。

This project is in the general area of analytical and surface chemistry and in the subfields of photochemistry and surface reaction dynamics. The research continues the Principal Investigator's studies of the photofragmentation, via internally repulsive states excited by an ultraviolet laser, of molecules adsorbed on metal and semiconductor surfaces. Photofragmentation, which generates radicals important in surface reactions, can proceed on these surfaces even in the presence of very fast (250 - 2500 femtoseconds) quenching of the excited states by energy transfer to the substrate. The role of faster charge transfer processes (5 - 50 fs) will be investigated by measuring the cross- sections, photofragment velocity and angular distributions, and polarization dependence for a series of small adsorbate molecules. Ultraviolet laser surface photochemistry is an important new area of fundamental research which has potentially broad applications in diverse technological fields such as semiconductor processing, solar energy conversion, chemical catalysis, and eye surgery. However, little is known about the fundamental mechanisms underlying the photochemical reactions. Both charge transfer and electron attachment have been identified as important reaction channels. Studies of the photofragmentation of adsorbed molecules will provide a highly specific probe of the dynamics of energy and charge transfer at interfaces.