分子光化学是星际化学、大气化学和环境化学的基础学科，在理论化学的发展中也起到了重要的作用。分子光化学研究中的典型三原子分子H2O和CO2在星际空间和地球大气层中广泛存在，其极紫外光解离过程不仅影响着我们对行星早期大气演化过程的理解，也影响着我们对地球环境变化的理解。半个世纪以来，H2O和CO2分子的光化学研究取得了惊人的进展，但是许多关键的科学问题还没有解开。大连自由电子激光光源是世界上首套专门运行于极紫外波段（50-150nm）的超强光源，而将自由电子极紫外光应用于分子光化学的研究在国际上也是首次。本项目拟建设完善基于大连极紫外自由电子激光的分子光化学实验线站，并利用实验线站装置对H2O和CO2分子进行系统性光化学研究。 这些实验有助于我们对H2O和CO2分子解离的完整图像的理解。

Molecular photochemistry is a fundamental subject for interstellar chemistry, atmospheric chemistry and environmental chemistry, is also important for theoretical chemistry developments. The H2O and CO2 molecules, the typical three-atom molecules for photochemistry, are ubiquitous in the interstellar space and in the Earth’s atmosphere. Their vacuum ultraviolet photochemistry is not only important for our understanding of the rise of oxygenic photosynthesis in Earth’s prebiotic primitive atmosphere, but also important for that of environmental changing. In the past fifty years, much development has been made for H2O and CO2 photochemistry, however, many major questions are still waiting to be revealed. Dalian Coherent Light Source (DCLS) is the first free-electron laser equipment operating at vacuum ultraviolet (50-150nm) region with extremely brilliance. It is also the first time to use the VUV free electron laser light for molecular photochemistry. In this project, we want to install the detection systems for Dalian Coherent Light- Molecular Photochemistry Line Station, and use this set-up to study the H2O and CO2 photochemistry systematically. Such systematic experiments can help us to understand the whole picture of H2O and CO2 dissociation.