Theoretical Studies of Ultrafast Electron Dynamics in Molecules Interacting with Intense Laser Pulses

实时捕捉和控制电子的重排和运动的能力被认为是物理、化学和生物学领域的一项重大挑战。超短激光脉冲允许直接探测(量子)物质在其量子演化的自然时间尺度上的瞬变性质。本项目旨在为如何识别、理解和控制激光诱导过程中电子波包动力学和分子中量子电子密度重排的变化提供理论见解。该项目的理论研究受到最近在阿秒(十亿分之一秒)时间尺度上的测量突破的推动，并将支持研究在高强度激光场影响下的分子电离过程、产生高能电磁辐射的高次谐波产生以及分子中的超快多电子动力学的实验。本项目的中心目标之一是应用描述电子波包的时间演化的方法，包括基态和激发态以及连续谱。含时密度泛函理论中的从头算数值模拟将探索分子中参与原子之间的电子共享和迁移过程中的量子动力学性质。特别令人感兴趣的是动力学中的非绝热电子局域化特征与强场电离和高次谐波产生等非线性过程中分子叠加态的独特特征之间的联系。(Bi)-圆偏振激光脉冲提供了一种控制和探索与环电流相关的动力学的方法，其中圆偏振光脉冲将其手性传递给分子，这表现为顺时针或逆时针电流。该研究项目的智力优势来自于理论和数值挑战的结合，这些挑战是在非微扰强度的外场中尝试解决多体问题时出现的，以及对依赖时间的高度非线性过程的数值模拟。预计该项目的成果将有助于理解在强激光场和阿秒科学存在的情况下分子系统中发生的光物理过程。该项目中的研究将与研究强激光场电离和高次谐波产生的实验工作直接相关，该实验工作致力于揭示简单和复杂系统中发生的电子动力学的细节。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The ability to capture and control in real time the rearrangement and motion of electrons is considered a grand challenge in physics, chemistry, and biology. Ultrashort laser pulses allow for direct probing of the transient properties of (quantum) matter on the natural time scales of its quantum evolution. The present project is directing toward providing theoretical insights into how to identify, understand, and control changes in the electron wavepacket dynamics and rearrangements in the quantum electron density in molecules during laser-induced processes. Theoretical studies within this project are motivated by recent breakthroughs in making measurements at the attosecond (one quintillionth of a second) time scale and will support experiments that study the molecular ionization process under the impact of high-intensity laser fields, high-order harmonic generation that produces high-energy electromagnetic radiation, and ultrafast multi-electron dynamics in molecules.One of the central goals of the present project is to apply methods that describe the time evolution of the electronic wavepacket including both ground and excited states as well as continuum. Ab initio numerical simulations within time-dependent density functional theory will explore the properties of quantum dynamics during the sharing and migration of electrons between participating atoms in a molecule. Of particular interest is the connection between nonadiabatic electron localization features in the dynamics and the unique signatures present for molecular superposition states for nonlinear processes such as intense field ionization and high harmonic generation. (Bi)-circularly polarized laser pulses offer a way to control and explore the ring current related dynamics where a circularly-polarized light pulse transfers its chirality to the molecule, which is manifested in either clockwise or counter-clockwise current. The intellectual merit of the research project arises from the combination of theoretical and numerical challenges, present when attempting the solution of the many-body problem in an external field of nonperturbative strength, and numerical simulations of time-dependent highly nonlinear processes. The results of the project are envisaged to contribute to understanding the photophysical processes occurring in molecular systems in the presence of intense laser fields and attosecond science. Studies within this project will be directly relevant to experimental work performed to study strong laser field ionization and high order harmonics generation devoted to uncovering the details of electron dynamics occurring in simple and complex systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.