Time-resolved photoemission from mass-selected metal clusters and their complexes with biomolecules at insulating surfaces

质量选择的金属簇及其与绝缘表面生物分子的复合物的时间分辨光电发射

• 批准号: 5405993
• 负责人: Professor Dr. Thorsten M. Bernhardt
• 金额: --
• 依托单位: Institut für Oberflächenchemie und Katalyse
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2003
• 资助国家: 德国
• 起止时间: 2002-12-31 至 2008-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5405993?language=en
• 关键词: Time; resolved; photoemission; mass; selected

Adding or removing one atom changes the physical and chemical properties of small metal clusters drastically. This is particularly true for small silver clusters with up to about 20 atoms. Especially the optical properties of supported and free atomic clusters of silver are intriguing and a strong current interest in this particular cluster system is due to two recent observations: (i) Irradiation of silver oxide particles leads to the photo-induced formation of stable distributions of surface-supported atomic silver clusters; (ii) a strong visible fluorescence was recently found, originating from unprecedented long-lived excited molecular states in atomic silver clusters. These properties uniquely qualify the small atomic silver clusters as a basis for advanced high-density optical storage (via (i)) and read-out (via (ii)) devices. However, neither the detailed electronic origin and cluster size dependence of the observed fluorescence is known up to now, nor any experimental data about the mechanism of the photoreductive formation of silver clusters. In order to get an insight into these fascinating properties of atomic silver clusters, we intend to apply the technique of time-resolved photoemission spectroscopy to a well-defined cluster-support system consisting of mass-selected silver clusters soft-landed onto an atomically flat insulating thin film of magnesia. The goal is to determine the electronic level structure of the supported silver clusters as a function of cluster size as well as the corresponding excited state lifetimes, in order to identify possible radiative and non-radiative transitions.

添加或删除一个原子会极大地改变小金属簇的物理和化学性质。对于最多含有 20 个原子的小银簇来说尤其如此。尤其是负载型和自由银原子簇的光学性质非常有趣，并且当前对这种特定簇系统的强烈兴趣归因于最近的两个观察结果：（i）氧化银颗粒的辐照导致表面负载原子银簇的稳定分布的光致形成； （ii）最近发现了强烈的可见荧光，源自原子银簇中前所未有的长寿命激发分子态。这些特性使小型原子银团簇成为先进高密度光存储（通过（i））和读出（通过（ii））设备的基础。然而，迄今为止，既不知道所观察到的荧光的详细电子起源和簇尺寸依赖性，也不知道有关银簇光还原形成机制的任何实验数据。为了深入了解原子银团簇的这些迷人特性，我们打算将时间分辨光电子能谱技术应用于一个明确的团簇支撑系统，该系统由软着陆到原子级平坦绝缘氧化镁薄膜上的质量选择的银团簇组成。目标是确定支撑银团簇的电子能级结构作为团簇尺寸的函数以及相应的激发态寿命，以便识别可能的辐射和非辐射跃迁。