氟/氯原子加水分子及其同位素取代反应的全维态-态量子动力学研究

Since the F/Cl+H2 problem were essentially solved, the F/Cl+H2O and its isotopically substituted reactions have become the most popular systems among dynamicist. They are also the prototype reactions to study vibrational mode/bond selectivity. Up to now, all the dynamical quantities were calculated by using either QCT or the reduced-dimensionality QM methods, which were not able to compete in accuracy with state-of-the-art experiments. In this project, full-dimensional global PES for the ground electronic state of F+H2O and Cl+H2O will be constructed using the neural networks method. The M-steps RPD and PCB scheme based time-dependent wave packet method will be developed to calculate differential cross sections for F/Cl+H2O reactions in full dimensions and investigate reaction resonance phenomenon in the process. We will also study the effect of reagent vibrational excitation on a state-to-state level. The reactant/product quantum state resolved information will improve our understanding of fundamental mechanisms of polyatomic reactions in vibrational excited states and test the applicability of the Polanyi’s rules. The successful accomplishment of the project will help us to exploit control of chemical reaction through reagent vibrational excitations, with the cooperation of high-resolution, crossed-molecular beam experiment.

F/Cl+H2反应之后，四原子反应F/Cl+H2O及其同位素取代物成为了动力学家们最感兴趣的体系，同时也是研究振动模式/化学键选择动力学的典型体系。目前对F/Cl+H2O反应的动力学计算大多使用准经典轨线方法或是简化维度的量子方法，缺少能在量子态分辨层次上与实验直接比较的精确理论结果。本项目中，我们将运用神经网络拟合方法构建F+H2O和Cl+H2O反应新的电子基态全维全域势能面。发展基于多步RPD方案和PCB方案的含时波包方法到原子-三原子体系，计算F/Cl+H2O反应的全维微分截面，研究反应过程中是否存在共振态现象及其机理。我们还将在态-态水平上研究H2O分子振动激发对反应的影响，通过反应物，过渡态和产物的量子态关联信息，理解多原子体系振动激发的本质机理，揭示Polanyi规则之外的普适规律。通过本项目的实施，结合高分辨的交叉分子束实验，帮助我们探索利用反应物振动激发控制化学反应。

在项目的资助下，我们按研究计划采用神经网络拟合方法，构建了Cl+H2O反应新的电子基态全维全域势能面。我们发展基于多步RPD和PCB方案的含时波包方法到原子-三原子体系中，在原则上解决了四原子反应散射问题；并用于计算H+H2O→H2+OH和H+D2O→HD+OD反应初始基态，第一对称和反对称伸缩振动激发态的全维微分截面，发现产生的OH只有很小一部分在v=1振动态上，从而证实了局域模式图像；还计算了Cl+H2O→HCl+OH和H2+OH→H+H2O反应的全维微分截面。此外，我们对最简单的经由瓦尔登翻转机理实现的取代反应：H'+CH4→CH3H'+H及其同位素类似物进行了精确的八维量子动力学计算，发现反应截面具有很强的正向二级同位素效应，而热速率常数表现出反向二级动力学同位素效应。我们还给出了包含超过一个重原子形成中间复合物的复杂四原子反应H+CO2→OH+CO不同初始态的总反应几率。这些研究不仅帮助我们深刻认识复杂体系的反应动力学，还揭示了多原子体系振动激发的本质机理。项目期间，共发表了5篇文章，包括1篇Nature Communications，1篇Chemical Science。