Low energy photon and electron excitations of molecules at metal surfaces and on molecular thin films

这是一个持续的研究项目，将调查、描述和解释涉及表面上光子和电子刺激化学过程的基本过程。在许多重要而有趣的化学系统中，这些受刺激的过程导致分子脱附（离开表面）、解离（分解成更小的碎片）以及与其他分子或表面的反应。这些过程实际上存在于广泛的其他物理过程中——例如，在许多重要的过程中，光被用来刺激表面化学反应性（表面光化学）。事实证明，在许多情况下，这种“光化学”实际上是由入射光产生的光电子引起的，也就是说，我们感兴趣的化学过程是由电子间接驱动的。该研究项目将使用超高真空（UHV）表面科学技术来研究这些光子和电子驱动的过程。精心制备的金属表面（主要是贵重的过渡金属）将被单层分子覆盖，然后由低能量的光子或电子束照射。所产生的化学过程可以单独研究，使用各种检测器来检查各种可能的结果。解吸离子由飞行时间带电粒子探测器检测；用四极杆质谱仪检测脱附中性物质；与共吸附分子发生反应的分子可以通过随后的热解吸来检测；与底物反应的分子碎片可以用俄歇电子能谱法检测。这项研究的结果在几个科学技术领域都有影响。目前这项工作的一个重点是研究电子如何从金属转移到分子薄膜上。这是新兴的“分子电子学”领域的关键一步。新材料可以使用特定的分子来选择所需的性能——这些类型的材料的一些例子已经商业化，例如用于显示器的有机led。希望这项工作能产生新的材料。

This is a continuing research program that will investigate, describe and explain the basic processes involved in photon and electron stimulated chemical processes on surfaces. In many important and interesting chemical systems, these  stimulated processes lead to molecular desorption (leaving the surface), dissociation (breaking into smaller fragments) and reaction with other molecules or the surface. These processes are actually present in a wide range of other physical processes- for instance in many important processes, light is used to stimulate surface chemical reactivity (surface photochemistry). It turns out that in many cases this `photochemistry' is actually caused by photoelectrons that are generated by the incident light, that is, the chemical processes of interest are driven indirectly by the electrons. This research program will study these photon and electron-driven processes using the techniques of ultra-high vacuum (UHV) surface science. Carefully prepared metal surfaces (primarily noble transition metals) will be covered with monolayer quantities of molecules that are then irradiated by a low energy beam of photons or electrons. The chemical processes that result can be studied individually using a variety of detectors that examine the various possible outcomes. Desorbing ions are detected by a time-of-flight charged particle detector; desorbing neutral species are detected by a quadrupole mass spectrometer; molecules that react with coadsorbed molecules can be detected by subsequent thermal desorption; molecular fragments that react with the underlying substrate can be detected by Auger electron spectroscopy. The results of this research have bearing in several areas of science and technology. A current focus in this work is studying how electrons are transferred from the metal into molecular thin films. This is a crucial step in the emerging field of 'molecular electronics'. New materials can be created using particular molecules to select desired properties- some examples of these types of materials are already commercially available, such as organic LEDs used in displays. It is hoped that new materials will result from this work.