Fiechter Marit R, Svoboda Vít, Wörner Hans Jakob
Laboratory of Physical Chemistry, ETH Zürich, 8093 Zurich, Switzerland.
Struct Dyn. 2023 Dec 15;10(6):064103. doi: 10.1063/4.0000213. eCollection 2023 Nov.
Photoelectron circular dichroism (PECD), the forward-backward asymmetry of the photoelectron angular distribution when ionizing randomly oriented chiral molecules with circularly polarized light, is an established method to investigate chiral properties of molecules in their electronic ground state. Here, we develop a computational strategy for predicting time-resolved PECD (TRPECD) of chemical reactions and demonstrate the method on the photodissociation of 1-iodo-2-methylbutane. Our approach combines multi-configurational quantum-chemical calculations of the relevant potential-energy surfaces of the neutral and singly ionized molecule with molecular-dynamics (AIMD) calculations. The PECD parameters along the AIMD trajectories are calculated with the aid of electron-molecule scattering calculations based on the Schwinger variational principle implemented in ePolyScat. Our calculations have been performed for two probe wavelengths (133 and 160 nm) accessible through low-order harmonic generation in gases. Our results show that the TRPECD is a highly sensitive probe of photochemical reaction dynamics. Most interestingly, the TRPECD is found to change sign multiple times along the photodissociation coordinate, in agreement with recent experiments on CHBrFI [Svoboda , "Femtosecond photoelectron circular dichroism of chemical reactions," Sci. Adv. , eabq2811 (2022)]. The computational protocol introduced in the present work is general and readily applicable to other chiral photochemical processes.
光电子圆二色性（PECD）是一种用于研究分子基态手性性质的成熟方法，它是指用圆偏振光电离随机取向的手性分子时，光电子角分布的前后不对称性。在此，我们开发了一种计算策略，用于预测化学反应的时间分辨光电子圆二色性（TRPECD），并在1-碘-2-甲基丁烷的光解离过程中演示了该方法。我们的方法将中性和单离子化分子相关势能面的多组态量子化学计算与分子动力学（AIMD）计算相结合。沿着AIMD轨迹的PECD参数是借助基于ePolyScat中实现的施温格变分原理的电子-分子散射计算来计算的。我们针对通过气体中的低阶谐波产生可获得的两个探测波长（133和160 nm）进行了计算。我们的结果表明，TRPECD是光化学反应动力学的一种高度灵敏的探针。最有趣的是，发现TRPECD在光解离坐标上多次改变符号，这与最近关于CHBrFI的实验结果一致[斯沃博达，“化学反应的飞秒光电子圆二色性”，《科学进展》，eabq2811（2022）]。本工作中引入的计算方案具有通用性，可很容易地应用于其他手性光化学过程。
