Computational Ultrafast X-ray Science

这项提议旨在开发一个用于模拟时间分辨X射线光谱仪的计算工具包。在这一提议中有三个主要的研究重点，它们集中在这个问题的重要方面，对于这些方面，现有的理论和计算技术不足以描述凝聚相中复杂分子在X射线领域的超快过程。特别是，这项提议将：1.)开发可以定量描述核心激发过程的电子结构的计算方法，特别是从价激发态，2。开发基于量子化学的方法来模拟这些动力学和化学过程在凝聚相中的可观察光谱特征，这是在X射线能量区工作的优势，以及3。模拟基本的分子动力学，这要求一个人将感兴趣的化学过程的从头算描述与环境(即溶剂)在促进特定反应结果中的作用结合在一起。这最后一个组成部分通常需要新的方法来将确定相关势能面的现代量子化学方法与直接量子动力学的方法联系起来。预计本提案中的工作将以与加拿大和国际机构的实验研究人员密切合作为特点，这些研究人员正在使用和开发时间分辨X射线光谱技术。理论和实验的紧密结合是我研究计划的一个标志，该领域目前建立的尖端实验合作者网络代表着一项重要的科学资产，将使这一研究计划得以成功实施。

This proposal aims to develop a computational toolkit for the simulation of time-resolved X-ray spectroscopies. There are three main research thrusts in this proposal that focus on important aspects of this problem for which the existing theoretical and computational techniques are insufficient to describe ultrafast processes in the X-ray domain for complex molecules in condensed phases. In particular, this proposal will: 1.) develop computational approaches that can quantitatively describe the electronic structure of core-excitation processes, particularly from valence excited states, 2.) development quantum chemistry based approaches to simulate the observable spectroscopic signatures of these dynamical and chemical processes in condensed phases, an advantage of working in the X-ray energy regime, and 3.) simulate the underlying molecular dynamics, which requires that one couple an ab initio description of the chemical processes of interest to the role of the environment (i.e. solvent) in facilitating particular reactive outcomes. This last component will generally require novel methods in linking modern quantum chemical approaches for determining the relevant potential energy surfaces to approaches in direct quantum dynamics. It is anticipated that the work in this proposal will be characterized by close collaboration with experimental researchers at Canadian and international institutions who are both employing and developing time-resolved X-ray spectroscopic techniques. The close coupling of theory and experiment is a hallmark of my research program and the now-established network of leading-edge experimental collaborators in this field represents a significant scientific asset that will enable the successful implementation of this research program.