MIES-studies on size-selected clusters deposited on oxide surfaces

本项目旨在通过亚稳态碰撞电子能谱(MIES)和紫外光电子能谱(UPS)相结合的方法研究氧化物表面纯团簇和连接团簇的电子结构，以了解它们的化学性质。在该项目的第一学期，我们将重点放在具有众所周知的、不同的和特定的化学性质的明确定义的金属簇合物上。我们将详细研究以下体系：(A)载于超薄氧化镁薄膜上的Au3sr、Au4和Au8：在这个例子中，我们首先用光谱表征了这三个团簇的电子态，并将所得结果与现有的从头计算进行了比较。其次，我们研究了02与这些团簇的结合行为以及吸附剂可能的活化作用。这些研究将提供关于这三个原子簇在CO氧化方面的不同化学性质的重要信息。(B)负载在超薄镁薄膜上的Pd原子：在这里，我们研究了通过碳酸盐的形成和/或CO和O2的共吸附在多大程度上发生了CO的氧化。在该项目的第一阶段，将在克劳斯塔尔技术大学建造一个高强度的亚稳态氦原子源。然后，这一来源将被整合到乌尔姆大学现有集群沉积实验的分析室中。在这个实验装置中，Miess研究所需的半球分析器已经可用。在未来，这些实验将扩展到其他系统。我们将在Mo(110)和Mo(112)上分别生长TiO_2和SiO_2薄膜，表征这些表面存在的缺陷，并研究不同载体材料上相同的团簇系统。

This project aims to study the electronic structure of pure and ligated clusters on oxide surfaces by means of the metastable impact electron spectroscopy, MIES, in combination with the ultraviolet photoelectron spectroscopy, UPS, in order to understand their chemical properties. We focus in the first term of the project on well-defined metal clusters with well-known, different and specific chemical properties. The following systems will be investigated in detail spectroscopically: (a) Au3Sr, Au4 und Au8 supported on ultrathin MgO-films: In this example we first characterize the electronic states of the three clusters spectroscopically and compare the obtained results with existing ab initio calculations. Second, we study the binding behavior of 02 to these clusters and a possible activation of the adsorbant. These studies will give important information on the different chemical properties of the three clusters with respect to the oxidation of CO. (b) Pd-atoms supported on ultrathin Mg0-films: Here we study to what extent the oxidation of CO occurs via carbonate formation and/or coadsorption of CO and 02. In the first phase of the project a highly intense source for metastable He atoms will be built at the Technical University of Clausthal. This source will then be integrated into the analysis chamber of the existing cluster deposition experiment at the University of Ulm. In this experimental setup the hemispherical analyzer, necessary for the MIESS studies, is already available. In future these experiments will be extended to other systems. We will grow thin Ti02 and Si02 films onto Mo(110) and Mo(112), respectively, characterize existing defects of these surfaces and study the same cluster systems on these different support materials.