Ultrafast single molecule videography with sub-Ångström resolution

具有亚埃分辨率的超快单分子摄像

• 批准号: 432343901
• 负责人: Professor Dr. Rupert Huber
• 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
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/432343901?language=en
• 关键词: Ultrafast; single; molecule; videography; sub

Functionalities of modern quantum materials, chemical reactions, and bio-chemical processes in a living cell are microscopically determined by the ultrafast dynamics of their molecular constituents. It has, thus, been an interdisciplinary goal of all natural sciences to gain direct access to the structure and motion of individual molecules. Steady-state scanning tunnelling microscopy (STM) has allowed researchers to perform imaging, spectroscopy, and manipulation with atomic resolution. Related experiments have yielded unique insights into the equilibrium electronic states of molecules. Resolving dynamics directly in the time domain, however, requires that excitations are confined to a short time window. Recently, we have joined forces to combine our expertise in sub-molecular STM imaging and subcycle lightwave electronics. In the first terahertz-driven STM (THz-STM) experiment of a single molecule, we combined sub-molecular spatial with subcycle temporal resolution and watched the vertical oscillations of a single pentacene molecule after its excitation by transient charging in THz-STM point-spectroscopy.The aim of this project is to systematically explore important ultrafast dynamics of individual molecules directly in space and time. To this end, we will introduce a new quality of THz-STM by extending our recently developed method of ultrafast THz-STM in four different directions: (i) We will take series of full images with varying pump-probe time delays, thereby recording the first molecular real-space slow-motion movies of various ultrafast molecular processes. We expect to establish the most direct and comprehensive picture of the ultrafast dynamic response inside individual molecules by immediate videography in space and time. (ii) Apart from electronic charging that we used so far to trigger vibrations, we anticipate yet more direct ways to excite dynamics of molecules, namely by exploiting the electric THz near-field of atomically sharp STM tips to exert an ultrafast atomically localized force transient that may prepare coherent structural wave packets. (iii) We intend to develop a novel concept of single-shot ultrafast action spectroscopy that will be able to follow single-molecule switching and reveal its unidirectional quantum probability and dynamics, being elusive to conventional pump-probe approaches. (iv) Finally, we intend to extend the portfolio of excitation stimuli from THz pulses to visible or ultraviolet excitation. This way, we may follow the important structure and dynamics of excitons in individual molecules with sub-Å spatial and femtosecond temporal resolution. We expect these key steps to open a new quality of observation, control, and understanding of single-molecule dynamics that have far-reaching consequences for chemistry, biochemistry, and physics, such as photocatalysis, the biology of vision, and ultracompact molecular circuits.

活细胞中的现代量子材料、化学反应和生物化学过程的功能在微观上是由其分子组成的超快动力学决定的。因此，直接了解单个分子的结构和运动已经成为所有自然科学的跨学科目标。稳态扫描隧道显微镜(STM)使研究人员能够以原子分辨率进行成像、光谱和操作。相关实验对分子的平衡电子态产生了独特的见解。然而，直接在时间域中解析动力学需要将激励限制在短时间窗口内。最近，我们联合起来，将我们在亚分子扫描隧道显微镜成像和亚周期光波电子学方面的专业知识结合起来。在首次太赫兹驱动的单分子扫描隧道显微镜(THz-STM)实验中，我们将亚分子的空间分辨率和亚周期时间分辨率结合起来，在THz-STM点光谱中观察了单个并五苯分子在瞬变电荷激发下的垂直振荡，旨在系统地直接在空间和时间上探索单个分子的重要超快动力学。为此，我们将引入一种新的THz-STM，将我们最近开发的超快THz-STM方法扩展到四个不同的方向：(I)我们将拍摄一系列具有不同泵浦-探测时间延迟的全图像，从而记录各种超快分子过程的第一个分子实空间慢动作电影。我们希望通过在空间和时间上的即时摄像，建立单个分子内部超快动态响应的最直接和最全面的图像。(Ii)除了我们到目前为止用来触发振动的电子充电之外，我们预计还有更直接的方法来激发分子的动力学，即通过利用原子尖锐的STM尖端的电子太赫兹近场来施加超快的原子定域力瞬变，这可能会制备出相干的结构波包。(Iii)我们打算发展一种新的概念，即单激发超快作用光谱，它将能够跟踪单分子开关，并揭示其单向量子几率和动力学，这是传统的泵浦-探测方法难以捉摸的。(4)最后，我们打算将激发刺激的组合从太赫兹脉冲扩大到可见光或紫外线激发。这样，我们就可以以亚空间和飞秒的时间分辨率跟踪单个分子中激子的重要结构和动力学。我们预计这些关键步骤将开启对单分子动力学的观察、控制和理解的新质量，这些动力学对化学、生物化学和物理具有深远的影响，如光催化、视觉生物学和超致密分子电路。