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Attosecond Electron Dynamics

阿秒电子动力学

基本信息

批准号：
1951317
负责人：
Stephen Leone
金额：
$ 60万
依托单位：
University of California-Berkeley
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-08-15 至 2023-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1951317&HistoricalAwards=false
关键词：
Attosecond Electron Dynamics

项目摘要

In this project funded by the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program of the Chemistry Division, Professor Stephen Leone of the University of California, Berkeley, uses sophisticated laser techniques to study some of the shortest time processes in molecules. Modern laser technology allows us to track the motion of the atomic nuclei in molecules as chemical reactions take place. However, the electrons that make up the bonds between atoms are thousands of times less massive than nuclei and therefore move much faster. This research project seeks to follow electron processes inside molecules that occur within 100 – 200 attoseconds (One attosecond is a decimal point followed by seventeen zeros and then a “1”). The fast measurements are accomplished by using laser light with wavelengths in the extreme ultraviolet and x-ray regions of the spectrum. The goal of this project is to characterize the motions of electrons in molecules undergoing chemical reactions, and perhaps catch the electron cloud in the moment when it is about to choose one reaction path over another. The research is important to understand the fundamental principles of charge flow (negative electrons and positive nuclei) and the breaking and reforming of chemical bonds for utilization of sunlight energy. Further benefits to society arise from the development of laser measurement capabilities that push the boundaries of short time durations in chemical dynamics using tools that require precision stability of lasers and optical platforms. These capabilities are certain find use in many areas of science and technology. In addition to the three graduate students who are directly involved in this project, members of the Leone research group engage in informal educational activities, including laboratory tours for high school students and teachers, and outreach events in coordination with the Lawrence Hall of Science.Ultrafast transient absorption in the extreme ultraviolet and X-ray, techniques developed in the Leone laboratory, are employed to make attosecond time-resolved dynamics measurements as a way to probe chemical dynamics that can separate electron dynamics timescales from nuclear motion. Electron correlation and superposition states play central roles in chemical processes on these short timescales. Attosecond probe pulses are produced via the process of high harmonic generation using carrier-envelope-phase stabilized driver laser pulses, and ultraviolet pulses are used to excite molecules by well-defined one-photon absorption. Core level transitions probed in reporter atoms are site- and oxidation-state specific, bond-length-sensitive, and electronic-state-dependent, providing an orbital-specific way to measure ultrafast dynamics. Objectives are to study attosecond and few-femtosecond time processes of curve crossing, passage through conical intersections, electronic and vibrational quantum mechanical superpositions, and charge migration recurrences. Molecules are chosen for study that have very different electronic configurations in multiple excited states or chemical environments around the molecule that are recognizable by spectroscopic means for charge flow, or for their relevance in chemical processing. The broader impacts of this work involve the development of tools that push the limits of time, important as both the dimensions and speed of devices decrease and as quantum principles in molecules are considered for computing architectures. Students who participate in this project learn an array of principles relevant for high technology professions that enable the speed and dimensions of ubiquitous electronic devices to decrease.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.

在这个由化学系化学结构、动力学和机制A(CSDM-A)计划资助的项目中，加州大学伯克利分校的Stephen Leone教授使用复杂的激光技术来研究分子中一些最短的时间过程。随着化学反应的发生，现代激光技术使我们能够跟踪分子中原子核的运动。然而，组成原子之间键的电子的质量比原子核小几千倍，因此移动速度要快得多。这项研究项目试图追踪分子内部发生在100-200阿秒内的电子过程(1阿秒是一个小数点，后面跟着17个0，然后是1)。快速测量是通过使用波长在光谱的极端紫外线和x射线区域的激光来完成的。这个项目的目标是描述电子在经历化学反应的分子中的运动，并可能在它即将选择一条反应路径而不是另一条反应路径的时刻捕捉到电子云。这项研究对于理解电荷流(负电子和正核)的基本原理以及光能利用中化学键的断裂和重整具有重要意义。激光测量能力的发展给社会带来了进一步的好处，这种能力使用需要激光和光学平台的精确稳定性的工具，突破了化学动力学中短期持续时间的界限。这些能力肯定会在许多科学和技术领域中使用。除了直接参与这一项目的三名研究生外，Leone研究小组成员还参加非正式教育活动，包括为高中生和教师参观实验室，并与劳伦斯科学馆协调举办外联活动。利用Leone实验室开发的在极端紫外线和X射线中的超快瞬变吸收技术，进行阿秒时间分辨动力学测量，以探索可以将电子动力学时间尺度与核运动分开的化学动力学。在这些短时间尺度上，电子关联和叠加态在化学过程中起着核心作用。阿秒探测脉冲是通过载波包络相位稳定的驱动激光脉冲产生高次谐波的过程产生的，而紫外光脉冲是通过明确的单光子吸收来激发分子的。在报告原子中探测的芯能级跃迁是位置和氧化态特定的，键长敏感的，电子态相关的，提供了一种测量超快动力学的轨道特定的方法。目的是研究曲线交叉、通过锥形交叉口、电子和振动量子力学叠加以及电荷迁移递归的阿秒和少飞秒时间过程。选择分子进行研究，这些分子在分子周围的多个激发态或化学环境中具有非常不同的电子配置，这些分子可以通过电荷流动的光谱手段识别，或者因为它们在化学处理中的相关性。这项工作的更广泛影响涉及到开发突破时间限制的工具，随着设备的尺寸和速度都减少，以及分子中的量子原理被考虑用于计算架构，这一点很重要。参与这个项目的学生学习一系列与高科技专业相关的原理，这些原理使无处不在的电子设备的速度和尺寸得以降低。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。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Nonresonant coherent amplitude transfer in attosecond four-wave-mixing spectroscopy

阿秒四波混频光谱中的非共振相干振幅传递

DOI：
10.1103/physreva.107.023526
发表时间：
2023
期刊：
Physical Review A
影响因子：
2.9
作者：
Gaynor, James D.;Fidler, Ashley P.;Kobayashi, Yuki;Lin, Yen-Cheng;Keenan, Clare L.;Neumark, Daniel M.;Leone, Stephen R.
通讯作者：
Leone, Stephen R.

Core-excited states of SF6 probed with soft-x-ray femtosecond transient absorption of vibrational wave packets