MRI: Acquisition of High-Power 100 kHz Laser for Recording Real-Time Movies of Ultrafast Molecular Reactions

MRI：采集高功率 100 kHz 激光来记录超快分子反应的实时电影

• 批准号: 2019150
• 负责人: Artem Rudenko
• 金额: $ 115.67万
• 依托单位: Kansas State University
• 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: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2019150&HistoricalAwards=false
• 关键词: MRI; Acquisition; Power; 100; kHz

The ability to predict and control the outcome of chemical reactions is essential for many areas of modern physics, chemistry and biology. This ability requires detailed knowledge of how individual atoms in molecules move to break, form, or rearrange chemical bonds between them during the reaction. This research project aims at obtaining high-resolution movies of such atomic motion. Since the atoms involved in chemical reactions move extremely fast, typically on a time scale of few tens of femtoseconds (one femtosecond is one millionth of a billionth of a second), ultrashort, femtosecond laser pulses are the only experimental tools capable of recording such movies in real time. However, because of the quantum nature of atoms and molecules, the outcome of any molecular reaction is not deterministic: even if one measurement precisely captures the positions of all atoms at a given time, the same measurement will have different outcomes if repeated several times, even under exactly identical conditions. The acquisition of a high-power laser system delivering a hundred thousand pulses (each shorter than 10 femtoseconds) per second will enable repeating such measurements millions of times, which is needed for the creation of a quantum-mechanical molecular movie. Each frame of a movie then reflects the probability of every possible configuration of atoms at different stages of the reaction, instead of a fixed picture of a molecule. Such movies will advance our understanding of fundamental chemical processes and provide input for applications in areas of national priority, ranging from efficient energy conversion and storage to synthesis of novel materials, drug design and molecular electronics. This project is jointly funded by the Major Research Instrumentation program and the Established Program to Stimulate Competitive Research (EPSCoR). Within this project, a broad range of photochemical processes, including photodissociation and isomerization, charge transfer reactions and formation of van der Waals clusters, will be studied. For each of these processes, the main scientific goal is to image the time-dependent molecular geometry and simultaneously characterize the evolving electronic structure of the molecule. This will be achieved by employing several complementary time-resolved techniques, including photoelectron spectroscopy and ion momentum imaging, inner-shell and laser-induced photoelectron diffraction, as well as ion beam techniques and Fourier-transform spectroscopy for characterization of the neutral fragments. For all these techniques, the key technical aspect facilitating simultaneous characterization of electronic and nuclear degrees of freedom will be the coincident detection of several reaction products, enabled by the high repetition rate of the acquired laser. At the same time, its high average power of several hundred watts will enable the efficient conversion of the emitted near-infrared radiation to a broad range of different wavelengths (from long-wavelength infrared to extreme ultraviolet and soft x-rays) needed for initiating and probing the reactions to be studied.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.

对于现代物理，化学和生物学的许多领域，预测和控制化学反应结果的能力至关重要。这种能力需要详细了解分子中单个原子在反应过程中如何移动，形成或重新排列化学键。该研究项目旨在获得这种原子运动的高分辨率电影。由于参与化学反应的原子的移动非常快，因此通常在几十秒钟的时间范围内（一秒钟的一百万秒，是十亿秒的一百万），因此超平秒的激光脉冲是唯一能够实时录制此类电影的实验工具。但是，由于原子和分子的量子性质，任何分子反应的结果均不确定性：即使一个测量精确地捕获给定时间的所有原子的位置，即使在完全相同的情况下，相同的测量结果也会重复几次。每秒提供了数十万脉冲（每秒远离10飞秒）的高功率激光系统的采集将使重复进行此类测量数百万次，这是创建量子力学分子电影所需的。然后，电影的每个框架都反映了反应不同阶段原子的每种可能构型的概率，而不是分子的固定图像。这样的电影将促进我们对基本化学过程的理解，并为国家优先领域的应用提供投入，从有效的能量转换和存储到合成新型材料，药物设计和分子电子产品。 该项目由主要的研究工具计划和启发竞争研究的既定计划共同资助。在该项目中，将研究广泛的光化学过程，包括光解异构和异构化，电荷转移反应以及范德华簇的形成。对于这些过程中的每个过程，主要的科学目标是成像时间依赖性的分子几何形状，并同时表征分子的不断发展的电子结构。这将通过采用几种互补的时间分辨技术来实现，包括光电子光谱和离子动量成像，内壳和激光诱导的光电子衍射以及离子束技术以及用于表征中性片段的表征的傅立叶传感器。对于所有这些技术，促进电子和核自由度同时表征同时表征的关键技术将是对几种反应产物的一致检测，这是由于获得的激光的高重复速率而实现的。同时，其数百瓦的高平均功率将能够有效地转换近红外辐射到广泛的不同波长（从长波长度到极端紫外线和柔软的X射线和柔软的X射线），以启动和探究该反应，以反映NSF的Inforthorial Mert。影响审查标准。