Experimental and theoretical studies into molecular photodynamics on the ultrafast dynamics

在过去的几十年里，亚皮秒激光技术的发展，特别是在自由电子激光（FEL）设备上，使得探索气相中各种小分子的超快光引发动力学成为越来越容易的方法。特别是，在泵浦探针实验中利用超快激光已经导致了“分子电影”的概念，它包括在短至几飞秒的时间尺度上跟踪分子动力学。通过发展全面的量子分子结构和轨迹理论，寻求这种动态实验的实验结果合理化。然而，在理想的精度水平上执行量子化学计算所花费的时间通常随着化学系统中自由度的大小和数量呈指数级增长。因此，开发能够最大限度提高量子化学计算精度并相应最小化运行时间的算法仍然是理论化学的一个重要研究主题。此外，通常还需要将理论计算的结果与给定实验的实验确定的参数综合起来，以便在理论和实验之间进行直接比较。该项目的目的是发展和实施现有的量子化学方法，以研究选择的小化学系统的超快分子动力学。另一个重点将是发展一种利用理论和实验设置知识来预测实验参数的方法，这些参数可以在超快激光设备上对这些分子进行实验时测量。具体来说，将理论与一组称为库仑爆炸成像（CEI）实验的结果相结合将是这项工作的重点；这是一种尚未在相当深入的理论中实现的东西。CEI实验涉及高电荷前体离子的快速破碎；然后通过二维探测器根据碎片的质量电荷比在空间和时间上检测碎片，其中在给定时间间隔内探测器上检测到的离子半径表示其在探测器平面内的速度。该项目还将包括参与运行和获取来自牛津郡阿尔忒弥斯激光设施等设施的CEI实验数据。该项目属于EPSRC物理科学研究领域。

Over the last few decades, developments in sub-picosecond laser technologies, especially at free-electron laser (FEL) facilities, have allowed for an increasingly accessible means of exploring the ultrafast photo-initiated dynamics of various small molecules in the gas-phase. In particular, utilising ultrafast lasers in pump-probe experiments has led to the concept of a "molecular movie", which encompasses following molecular dynamics on timescales as short as a few femtoseconds. Through developing comprehensive quantum molecular structure and trajectory theories for such experiments, experimental outcomes of such dynamical experiments are sought to be rationalised. However, the time taken to perform quantum chemical calculations at a desired level of accuracy often scales exponentially with the size and number of degrees of freedom in a chemical system. Hence, developing algorithms which maximise the accuracy of quantum chemical calculations yet which correspondingly minimise the run-time remains an important research theme in theoretical chemistry. Further to this, there often remains the need to synthesise the results of theoretical calculations with experimentally determined parameters for a given experiment so as to allow for a direct comparison between theory and experiment. The aim of this project is to develop and implement existing quantum chemical methods in order to study the ultrafast molecular dynamics of select small chemical systems. Another main focus will be developing a means of using theory and a knowledge of experimental setup to predict experimental parameters which can be measured at experiments to be conducted on such molecules at ultrafast laser facilities. Specifically, integrating theory with the outcomes of a set of experiments called Coulomb explosion imaging (CEI) experiments will be a focus of this work; this is something which has not yet been achieved at a considerable depth of theory. CEI experiments involve the rapid fragmentation of a highly-charged precursor ion; fragments are then detected spatially and temporally according to their mass-to-charge ratios by two-dimensional detector, where the radius of an ion detected within a given time-interval on the detector is indicative of its velocity within the detector plane. This project will also involve taking part in running and acquiring data from CEI experiments at facilities such as the Artemis laser facility in Oxfordshire. This project falls within the EPSRC Physical Sciences Research area.