A New Effect in Ultrafast X-ray Scattering

超快X射线散射的新效应

• 批准号: EP/V049240/2
• 负责人: Adam Kirrander
• 金额: $ 56.3万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FV049240%2F2
• 关键词: New; Effect; Ultrafast; ray; Scattering

Light triggers many important chemical reactions. These include photosynthesis (converting sunlight to chemical energy), human vision (detecting photons via light-induced changes in molecules), and new technologies such as photodynamic therapy for cancer, photocatalysis, fluorescent tags for healthcare diagnostics, and photovoltaics. Light-triggered processes in molecules are difficult to study experimentally and involve a complex interplay of concerted changes in molecular structure and rapid rearrangements of the electrons in the molecule. Conical intersections play a decisive role for the outcome of photochemical reactions, analogous to that of a transition state in standard ground-state chemistry. These are regions on photochemical pathways where molecules can transition efficiently between electronic states. Being able to map the path of molecules through conical intersections would open avenues to controlling photochemical reactivity via modification of excited state dynamics. To achieve this we must simultaneously observe the electronic characteristics of the molecule and the corresponding changes in molecular structure. The challenge is compounded by the short timescales involved, on the order of femtoseconds. Notably, there are as many femtoseconds in a second as there are seconds in 30 million years. In contrast, standard techniques for structural determination require long observation times. New facilities known as X-ray Free-Electron Lasers (XFELs) deliver extremely short pulses of intense high-energy x-ray photons, making completely new types of measurements possible. In recent work, we have demonstrated that we can track the changes in molecular structure in excited molecules and, in separate experiments, detect the nearly instantaneous re-arrangement of electrons when molecules absorb light. Exploiting these advances, the proposed project will develop measurements that track the motion of electrons alongside the motion of the nuclei, allowing conical intersections to be identified, and the structure of molecules at conical intersections to be determined. The resulting experimental technique will yield a powerful tool for fundamental research and provide images of electrons and nuclei that can be used to customise photoactive molecules, ultimately contributing to new technologies in catalysis, new cancer treatments, and energy harvesting from sunlight.

光引发许多重要的化学反应。这些包括光合作用（将阳光转化为化学能），人类视觉（通过光诱导的分子变化检测光子），以及新技术，如用于癌症的光动力疗法，荧光标记，用于医疗诊断和光子学。光引发的分子过程很难在实验上研究，涉及分子结构的协调变化和分子中电子的快速重排的复杂相互作用。圆锥形交叉点对于光化学反应的结果起着决定性的作用，类似于标准基态化学中的过渡态。这些是光化学途径上的区域，分子可以在电子状态之间有效地转换。能够绘制出分子通过圆锥形交叉点的路径，将为通过修改激发态动力学来控制光化学反应开辟道路。要做到这一点，我们必须同时观察分子的电子特性和分子结构的相应变化。所涉及的短时间尺度（飞秒量级）加剧了这一挑战。值得注意的是，一秒中的飞秒数相当于3000万年中的秒数。相比之下，用于结构测定的标准技术需要长的观察时间。被称为X射线自由电子激光器（XFEL）的新设备提供极短脉冲的强高能X射线光子，使全新类型的测量成为可能。在最近的工作中，我们已经证明，我们可以跟踪激发分子中分子结构的变化，并在单独的实验中，检测到分子吸收光时电子的几乎瞬时重新排列。利用这些进展，拟议的项目将开发跟踪电子运动与原子核运动的测量方法，从而识别圆锥形交叉点，并确定圆锥形交叉点处的分子结构。由此产生的实验技术将为基础研究提供强大的工具，并提供可用于定制光活性分子的电子和原子核图像，最终有助于催化，新癌症治疗和太阳能收集的新技术。

项目成果

Mapping the photochemistry of cyclopentadiene: from theory to ultrafast X-ray scattering

• DOI: 10.1039/d2fd00176d
• 发表时间: 2023-02-10
• 期刊: FARADAY DISCUSSIONS
• 影响因子: 3.4
• 作者: Bertram，Lauren;Weber，Peter M.;Kirrander，Adam
• 通讯作者: Kirrander，Adam

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.

Efficient Computation of Two-Electron Reduced Density Matrices via Selected Configuration Interaction.

通过选定的配置相互作用有效计算二电子约简密度矩阵。

• DOI: 10.1021/acs.jctc.2c00738
• 发表时间: 2022-11-08
• 期刊: JOURNAL OF CHEMICAL THEORY AND COMPUTATION
• 影响因子: 5.5
• 作者: Coe, Jeremy P.;Carrascosa, Andres Moreno;Simmermacher, Mats;Kirrander, Adam;Paterson, Martin J.
• 通讯作者: Paterson, Martin J.

Automatic Clustering of Excited-State Trajectories: Application to Photoexcited Dynamics.

• DOI: 10.1021/acs.jctc.3c00776
• 发表时间: 2023-09-26
• 期刊: JOURNAL OF CHEMICAL THEORY AND COMPUTATION
• 影响因子: 5.5
• 作者: Acheson, Kyle;Kirrander, Adam
• 通讯作者: Kirrander, Adam

Towards high-resolution X-ray scattering as a probe of electron correlation

• DOI: 10.1039/d2cp02933b
• 发表时间: 2022-10-04
• 期刊: PHYSICAL CHEMISTRY CHEMICAL PHYSICS
• 影响因子: 3.3
• 作者: Carrascosa, Andres Moreno;Coe, Jeremy P.;Kirrander, Adam
• 通讯作者: Kirrander, Adam