Collaborative Research: Probing Attosecond Charge Dynamics in Atoms and Molecules

合作研究：探测原子和分子中的阿秒电荷动力学

• 批准号: 1806575
• 负责人: Zenghu Chang
• 金额: $ 21万
• 依托单位: The University of Central Florida Board of Trustees
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1806575&HistoricalAwards=false
• 关键词: Collaborative; Research; Probing; Attosecond; Charge

An ability to identify, tag and follow unambiguously quantum trajectories of electrons in molecular systems is central to addressing questions that are key to unlocking solutions to an array of contemporary scientific and technical challenges - understanding the chemistry of interstellar media, reducing our carbon footprint, enabling efficient, clean energy sources and controlling dynamics in biological molecules are just a few examples. Light-induced charge dynamics, for example, is ubiquitous in catalysis, photosynthesis, the photovoltaic effect, radiation damage in biomolecules and atmospheric chemistry. With clock speeds of order 1 femtosecond (10^-15 s), the energy flow and correlated dance between electrons and atomic nuclei require subfemtosecond temporal resolution (e.g., 100 attosecond = 0.1 femtosecond) and carefully-designed experimental techniques to track reliably. The University of Central Florida (UCF) - University of Maryland (UMD) collaboration has assembled the instrumentation and personnel to study such dynamics in important prototype molecules. Specifically, charge dynamics will be probed experimentally by transient changes in the absorption spectrum of so-called core-level states (those closest to the nucleus) of the carbon atom. These novel measurements may lead to new understanding of key physical concepts, clearer pictures of fundamental processes and novel ways to control electron dynamics. Employing a few-cycle infrared intense (IR) pump and an attosecond soft X-ray probe in the water window (240 to 330 eV in this study) for transient absorption of core-level carbon atoms, the University of Central Florida (UCF) - University of Maryland (UMD) collaboration is investigating ultrafast dynamics in two important hydrocarbons. One set of experiments is dedicated to tracking structural changes induced by the IR pulse in methane as it loses hydrogen atoms (deprotonization) with subfemtosecond temporal resolution. The second study focuses on IR-induced isomerization of acetylene into vinilydene also with subfemtosecond resolution. One novelty of these studies rests in a forty-fold improvement in temporal resolution over previous transient absorption measurements in the water window. The UCF-UMD collaboration is ideally suited to carry out this investigation because of the investigators' long history in building and operating state-of-the-art attosecond lasers (UCF) and probing and controlling atomic and molecular dynamics (UMD). To ensure the best interpretation of the experimental results, the team works closely with UCF theorists running contemporary numerical codes such as XCHEM and MESA to help analyze the data. The results will provide new insight into time-dependent structure changes and correlated electron motion induced by strong external perturbation, which potentially could reveal innovative ways to control electron dynamics.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.

识别、标记和跟踪分子系统中电子的明确量子轨迹的能力对于解决问题至关重要，而这些问题是解决一系列当代科学和技术挑战的关键——了解星际介质的化学性质，减少我们的碳足迹，使高效、清洁的能源和控制生物分子的动力学只是几个例子。 例如，光诱导电荷动力学在催化、光合作用、光伏效应、生物分子辐射损伤和大气化学中普遍存在。在时钟速度为 1 飞秒（10^-15 秒）的情况下，电子和原子核之间的能量流和相关舞蹈需要亚飞秒时间分辨率（例如，100 阿托秒 = 0.1 飞秒）和精心设计的实验技术来可靠地跟踪。 中佛罗里达大学 (UCF) - 马里兰大学 (UMD) 合作组装了仪器和人员来研究重要原型分子的此类动力学。 具体来说，电荷动力学将通过碳原子所谓的核心级状态（最接近原子核的状态）吸收光谱的瞬态变化来进行实验探测。这些新颖的测量可能会带来对关键物理概念的新理解、更清晰的基本过程图像以及控制电子动力学的新方法。 中佛罗里达大学 (UCF) 在水窗口（本研究中为 240 至 330 eV）中采用了几个周期红外强 (IR) 泵和阿秒软 X 射线探头来瞬时吸收核心层碳原子- 马里兰大学 (UMD) 合作正在研究两种重要碳氢化合物的超快动力学。 一组实验致力于以亚飞秒时间分辨率跟踪甲烷中红外脉冲在失去氢原子（去质子化）时引起的结构变化。第二项研究的重点是红外诱导的乙炔异构化为亚乙烯基，同样具有亚飞秒分辨率。 这些研究的一项新颖之处在于时间分辨率比之前在水窗中的瞬态吸收测量提高了四十倍。 UCF-UMD 合作非常适合开展这项研究，因为研究人员在建造和操作最先进的阿秒激光器 (UCF) 以及探测和控制原子和分子动力学 (UMD) 方面拥有悠久的历史。 为了确保对实验结果的最佳解释，该团队与 UCF 理论家密切合作，运行 XCHEM 和 MESA 等当代数值代码来帮助分析数据。 研究结果将为强外部扰动引起的随时间变化的结构变化和相关电子运动提供新的见解，这有可能揭示控制电子动力学的创新方法。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准。

项目成果

Generation of few-cycle multi-millijoule 2.5 μm pulses from a single-stage Cr2+:ZnSe amplifier

从单级 Cr2 :ZnSe 放大器生成几个周期的多毫焦耳 2.5 μm 脉冲

• DOI: 10.1038/s41598-020-64330-8
• 发表时间: 2020
• 期刊: Scientific Reports
• 影响因子: 4.6
• 作者: Wu, Yi;Zhou, Fangjie;Larsen, Esben W.;Zhuang, Fengjiang;Yin, Yanchun;Chang, Zenghu
• 通讯作者: Chang, Zenghu

Signal Retrieval With Measurement System Knowledge Using Variational Generative Model

使用变分生成模型利用测量系统知识进行信号检索

• DOI: 10.1109/access.2020.2978435
• 发表时间: 2020
• 期刊: IEEE Access
• 影响因子: 3.9
• 作者: Zhu, Zheyuan;Sun, Yangyang;White, Jonathon;Chang, Zenghu;Pang, Shuo
• 通讯作者: Pang, Shuo

Attosecond science based on high harmonic generation from gases and solids

• DOI: 10.1038/s41467-020-16480-6
• 发表时间: 2020-06-02
• 期刊: NATURE COMMUNICATIONS
• 影响因子: 16.6
• 作者: Li, Jie;Lu, Jian;Chang, Zenghu
• 通讯作者: Chang, Zenghu

Attosecond chirp compensation in water window by plasma dispersion

• DOI: 10.1364/oe.26.033238
• 发表时间: 2018-12-10
• 期刊: OPTICS EXPRESS
• 影响因子: 3.8
• 作者: Chang, Zenghu

Enhancing keV high harmonic signals generated by long-wave infrared lasers

• DOI: 10.1364/osac.2.002131
• 发表时间: 2019-04
• 期刊: OSA Continuum
• 影响因子: 1.6
• 作者: Z. Chang