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，我们旨在证明并应用一种新的实验概念来研究时间分辨率在100秒以下的表面上的超快结构动力学。在结构信息旁边，检测到的瞬态光电信号将同时携带有关表面电子系统的激发和弛豫的信息，从而潜在地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，我们将重点研究酞菁分子在贵金属表面的亚单层吸附。在静态ARPES实验中，对这种吸附表面系统的不同代表所报道的独特的低能光电子衍射图为检查所提出概念的能力和局限性提供了理想的测试平台。此外，我们期望结构动力学和载流子动力学的结合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）产生探测光电子时，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，Ekin < 2 eV的光电子的本征非常低的动能将限制我们的研究，由于泵浦诱导的寄生电子发射产生的信号背景，我们的研究仅限于小而中等的泵浦影响。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，这样也可以在明显更高的泵浦影响下进行实验。在这种影响下，我们期望能够在吸附层中触发结构相变。