Electron Densities and Electron Correlations by X-Ray Scattering

X 射线散射的电子密度和电子相关性

• 批准号: 2309434
• 负责人: Peter Weber
• 金额: $ 52.8万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-05-01 至 2026-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2309434&HistoricalAwards=false
• 关键词: Electron; Densities; Correlations; Ray; Scattering

With support from the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program in the Division of Chemistry, Professor Peter M. Weber of Brown University is using x-ray scattering techniques to observe how electrons orbit the atomic nuclei of molecules. Electron orbitals are the places where electrons are preferentially located and have distinct shapes that depend upon the arrangement of the nuclei and the electron energy. In molecules with more than one electron, repulsions between the electrons affect the orbital shape. In short, the motion of an electron depends upon the motion of all the other electrons, giving rise to correlations in electron motion that profoundly affect all molecular properties. For example, when molecules absorb light, an electron is promoted to a higher energy state and the distributions and correlations change, resulting in a multitude of photochemical phenomena. Observing these changes are difficult though, given the speed with which electrons move. Professor Weber and his students will use time-resolved x-ray scattering methods to measure precise excited state molecular structures, electron density distributions and electron-electron pair correlations that are central to molecular properties. Their discoveries could lead to new benchmarks that aid the continued development of quantum chemistry computer programs. Since quantum chemistry calculations are used throughout the molecular sciences, the project could have far-reaching ramifications and impact in many related fields. The project will train students in advanced experimental methodologies and complex computer simulations.Time-resolved X-ray scattering experiments will be conducted at the Linac Coherent Light Source X-Ray Free Electron Laser of SLAC National Accelerator Laboratory. Femtosecond laser pulses will be used to excite molecules to excited electronic states. After a short time-delay, an ultrashort x-ray pulse from the free electron laser is scattered off the molecules. The measured scattering signals are compared to theoretical ones derived from computed electron density distributions and correlations. The project will extend the x-ray methods used to determine molecular structures and electron densities of ground states to the excited state and include electron-electron correlations. The studies will focus on a selection of model systems with different p-electron characters and electron correlations. Codes for simulating scattering patterns directly from computational methods and an iterative refinement process have been developed and will be applied. The experimentally measured densities, correlations and structures are compared to the results of high-level computational chemistry methods and serve as benchmarks for the quantum chemistry calculations. The studies will improve our understanding of molecular structures and chemical reactivity, which in turn determines many chemical and material properties.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.

在化学结构，动力学和机制A（CSDM-A）计划的支持下，布朗大学的Peter M. Weber教授正在使用X射线散射技术来观察电子如何绕分子的原子核绕。电子轨道是电子优先位置并且具有不同形状的地方，取决于核和电子能的排列。在具有多个电子的分子中，电子之间的排斥会影响轨道形状。简而言之，电子的运动取决于所有其他电子的运动，从而产生了电子运动的相关性，从而深刻影响所有分子特性。例如，当分子吸收光时，电子被促进到较高的能量状态，并且分布和相关性变化，从而导致多种光化学现象。但是，考虑到电子移动的速度，观察这些变化很困难。 韦伯教授和他的学生将使用时间分辨的X射线散射方法来测量精确的激发态分子结构，电子密度分布以及电子对分子特性核心的电子对相关性。他们的发现可能导致新的基准测试，以帮助量子化学计算机计划的持续开发。由于在整个分子科学中都使用了量子化学计算，因此该项目可能在许多相关领域都具有深远的影响和影响。该项目将培训学生采用高级实验方法和复杂的计算机模拟。将在SLAC国家加速器实验室的Linac Cooherent Light Soughts Free Electron激光器上进行时间分辨的X射线散射实验。飞秒激光脉冲将用于激发激发电子状态的分子。短时间延迟后，来自游离电子激光器的超短X射线脉冲散布在分子上。将测得的散射信号与从计算的电子密度分布和相关性得出的理论散射信号进行了比较。该项目将扩展用于确定基态分子结构和电子密度的X射线方法到激发态，并包括电子电子相关性。研究将集中于具有不同P电子字符和电子相关性的模型系统的选择。已经开发了直接从计算方法中模拟散射模式的代码，并将应用并将应用。将实验测量的密度，相关性和结构与高级计算化学方法的结果进行比较，并作为量子化学计算的基准。这些研究将提高我们对分子结构和化学反应性的理解，这反过来决定了许多化学和材料特性。该奖项反映了NSF的法定任务，并使用基金会的智力优点和更广泛的影响审查标准，被认为值得通过评估来提供支持。

项目成果

Extracting the electronic structure signal from X-ray and electron scattering in the gas phase

• DOI: 10.1107/s1600577524000067
• 发表时间: 2024-03-01
• 期刊: JOURNAL OF SYNCHROTRON RADIATION
• 影响因子: 2.5
• 作者: Northey，Thomas;Kirrander，Adam;Weber，Peter M.
• 通讯作者: Weber，Peter M.