Studying Correlated Electron Dynamics in Molecules and Materials with Isolated Attosecond Pulses

电子在大多数自然现象和实验室现象中起着基本的作用。这些基本粒子非常轻且灵活——它们可以在“阿秒”的时间尺度上在原子、分子和材料内部移动，“阿秒”是十亿分之一秒的十亿分之一。为了理解物理、化学和生物过程的功能，能够解析和控制潜在的快速电子运动是很重要的。新发明的阿秒技术正是提供了这样一个机会，它使用光脉冲来频闪电子的动力学。然而，该领域的大多数初步研究都是在原子和小分子等简单系统上进行的。该项目支持的研究人员将开发和扩展阿秒技术，以研究一个或多个电子相互作用的复杂分子和材料。沿着这些方向的成功将为直接研究与光收集和能量储存相关的许多生化和纳米材料过程提供机会。因此，拟议的计划将通过在物理学领域与化学、生物学和材料科学领域之间建立桥梁来推进科学水平。该项目还将在这一新兴的跨学科研究领域培养具有不同背景的下一代科学家。电子相关往往主导着光激发分子和纳米材料的激发和弛豫动力学，体现在重要的自然和实验室过程中的能量和电荷再分配机制中，如光合作用、DNA的修复和损伤、分子-半导体界面的能量储存等。本研究项目旨在利用各种类型的超快光谱研究相关驱动的物理和化学现象。这些研究所需的高时间分辨率将通过使用双光门控或类似方案产生孤立的阿秒脉冲来实现。该项目的科学目标将是：(1)研究多原子分子（如苯基分子）中的相干电荷迁移动力学，(2)研究电子波包动力学中的相干性和退相干机制的起源，(3)探索碳纳米材料（如石墨烯）中高能激子的产生和动力学。这些目标将在培养阿秒物理领域的研究生和本科生的同时实现。两种强大的实验技术将在拟议的测量中使用：速度图成像和阿秒瞬态吸收。提案中概述的调查将为更好地理解自然现象和实际相关现象的内部运作提供基础。与理论家的合作将在解释在这一未知领域获得的结果方面发挥关键作用，可能导致新的理论模型的发展。

Electrons play a fundamental role in most natural and laboratory phenomena. These elementary particles are extremely light and agile--they can move inside atoms, molecules and materials on the timescale of "attoseconds," which is a billionth of a billionth of a second. To understand the functioning of physical, chemical, and biological processes, it is important to be able to resolve and control the underlying fast electronic motion. Newly devised attosecond techniques provides exactly such an opportunity, using light pulses to strobe the dynamics of electrons. However, most initial studies in this field have been conducted on simple systems like atoms and small molecules. The researchers supported by this program will develop and extend attosecond techniques to the study of complex molecules and materials, where one or more electrons are interacting with each other. Success along these directions will open up opportunities for direct investigation of many biochemical and nanomaterial processes relevant for light harvesting and energy storage. The proposed program will therefore advance the state of science by building bridges between the field of physics, and those of chemistry, biology, and material sciences. The project will also train the next generation of scientists belonging to diverse backgrounds in this emerging and interdisciplinary research field.Electronic correlation often dominates the excitation and relaxation dynamics of photo-excited molecules and nanomaterials, manifesting itself in the energy and charge redistribution mechanisms in important natural and laboratory processes, such as photosynthesis, repair and damage or DNA, energy storage at molecule-semiconductor interfaces etc. This research project aims at the investigation of correlation-driven physical and chemical phenomena using various types of ultrafast spectroscopy. The high temporal resolution required for these studies will be achieved through the generation of isolated attosecond pulses using double optical gating or similar schemes. The scientific objectives of this program will be to: (1) investigate coherent charge migration dynamics in polyatomic molecules, such as those consisting of a phenyl group, (2) study the coherence in electron wavepacket dynamics and the origin of decoherence mechanisms, and (3) probe the generation and dynamics of high energy excitons in carbon nanomaterials (e.g. graphene). These objectives will be achieved while training graduate and undergraduate students in the field of attosecond physics. Two powerful experimental techniques will be utilized in the proposed measurements: velocity map imaging and attosecond transient absorption. The investigations outlined in the proposal will provide the building blocks for developing a better understanding of the inner-workings of natural and practically relevant phenomena. Collaborations with theorists will play crucial role in the interpretation of results obtained in this unchartered territory, potentially leading to the development of new theoretical models.