Time-resolved low energy photoelectron diffraction for the study of surface structural dynamics with sub-100 fs temporal resolution

用于研究表面结构动力学的时间分辨低能光电子衍射，时间分辨率低于 100 fs

• 批准号: 433458487
• 负责人: Professor Dr. Michael Bauer
• 金额: --
• 依托单位: Institut für Experimentelle und Angewandte Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/433458487?language=en
• 关键词: Time; resolved; low; energy; photoelectron

Based on the diffraction of low energy photoelectrons we aim for proving and applying a novel experimental concept for the study of ultrafast structural dynamics at surfaces with sub-100 fs temporal resolution. Next to structural information, the detected transient photoemission signal will at the same time carry information about excitation and relaxation of the involved surface electronic system potentially allowing for a direct correlation of structural and carrier dynamics at surfaces. Within our studies we will focus on sub-monolayer adsorption of phthalocyanine molecules on noble metal surfaces. The distinctive low energy photoelectron diffraction patterns that have been reported for different representatives of this adsorbate-surface system in static ARPES experiments represent an ideal test bed for the examination of the capabilities and limitations of the proposed concept. Furthermore, we expect that the combined interrogation of structural and carrier dynamics can shed new light into the complex interaction mechanisms governing the multifaceted properties of this metal-organic interface class. Two different experimental configurations will be realized and tested within the project: In using 70 fs NUV laser pulses (6 eV) for the generation of the probing photoelectrons we will be able to probe structural and carrier dynamics at an ultimate temporal resolution below 100 fs. The intrinsic very low kinetic energies of the photoelectrons of Ekin < 2 eV will, however, limit our studies to small and moderate pump fluences due to a signal background arising from pump-induced parasitic electron emission. In an alternative configuration we will use 18 eV vacuum ultraviolet pulses from a HHG source so that also experiments at significantly higher pump fluences will become possible. In this fluence regime we expect to be able to trigger also structural phase transitions in the adsorbate layer.

基于低能光电子的衍射，我们的目标是证明和应用一种新颖的实验概念，用于研究时间分辨率低于 100 飞秒的表面超快结构动力学。除了结构信息之外，检测到的瞬态光电发射信号将同时携带有关所涉及表面电子系统的激发和弛豫的信息，可能允许表面结构和载流子动力学的直接关联。 在我们的研究中，我们将重点关注贵金属表面上酞菁分子的亚单层吸附。在静态 ARPES 实验中，该吸附表面系统的不同代表已报告的独特的低能光电子衍射图案代表了检查所提出概念的能力和局限性的理想试验台。此外，我们期望对结构和载流子动力学的综合研究可以为控制这种金属有机界面类的多方面性质的复杂相互作用机制提供新的线索。该项目将实现和测试两种不同的实验配置：在使用 70 fs NUV 激光脉冲 (6 eV) 生成探测光电子时，我们将能够以低于 100 fs 的最终时间分辨率探测结构和载流子动力学。然而，由于泵浦引起的寄生电子发射产生的信号背景，Ekin 光电子固有的非常低的动能 < 2 eV 将限制我们的研究仅限于小而中等的泵浦通量。在另一种配置中，我们将使用来自 HHG 源的 18 eV 真空紫外脉冲，以便在显着更高的泵浦通量下进行实验也将成为可能。在这种注量状态下，我们期望能够触发吸附层中的结构相变。