基于极紫外相干光源的分子解离动力学研究

Photodissociation has been attracted much attention because it plays the important role in simulating complex chemical reaction systems associated with atmospheric chemistry, combustion chemistry, and interstellar chemistry. Since the invention of the laser in 1960, photodissociation dynamics has obtained series of remarkable achievements. However, due to lacking of a better vacuum ultraviolet(VUV) light source, photodissociation of H2S and OCS molecules haven’t yet to make a major breakthrough in the VUV region. At present, the successful development of "Dalian coherent light source" with tunable (50~180nm) and high brightness will bring hope for VUV photolysis kinetics. This project intends to combine of this advanced light source and the experimental apparatus with H atom Rydberg tagging time-of-flight method and time slice ion velocity imaging techniques, and to achieve the VUV phdissociation of small molecular systems such as H2S/OCS. Though this study, it will reveal the dissociation kinetic behavior of small molecules in the high electron excited state and the effect of the initial excited state on the microscopic dissociation mechanism, and provide effective basis for solving the problem of sulfur pollution.

光解因在模拟大气化学、燃烧化学以及星际化学相关的复杂化学反应体系中所发挥的重要作用而一直以来备受人们的关注。自1960年激光发明以来，光解动力学研究更是取得了令人瞩目的成就。然而，由于缺少理想的真空紫外光源，诸如H2S、OCS等分子在真空紫外波段的光解实验研究尚未取得大的突破。目前，具有高亮度、可调谐（50~180nm）的“大连相干光源”的成功研制为深入研究真空紫外光解动力学带来了希望。本项目拟凭借这一极紫外相干光源的诸多优势，将之与兼具里德堡态氢原子飞行时间谱及时间切片离子速度成像技术的实验装置相结合，实现以H2S、OCS为代表的分子真空紫外多通道解离动力学的系统性研究，从中揭示分子高电子激发态解离动力学行为及不同初始激发态对于微观解离机制的影响，进而为有效解决硫污染问题提供基础研究依据。

自由电子激光的诞生为分子真空紫外光解动力学实验研究提供了一个不可多得的工具。过去四年来，在自然科学基金面上项目的资助下，我们成功将“大连相干光源”引入兼具两种探测技术的实验系统，为深入研究分子真空紫外多通道解离动力学提供了技术支撑和实验平台。在此基础上，我们利用这一新实验系统顺利实现了CO2和OCS分子初始态选择的真空紫外解离动力学研究。从中获取了丰富的诸如产物总平动能谱、振动态布居、空间角分布等动力学信息。本项目所取得的实验成果不仅有助于人们了解CO2和OCS分子在高电子激发态下的解离图景及微观机理，也为今后理论上进一步研究CO2和OCS分子在真空紫外波段的解离过程提供了重要的实验依据。