基于X射线散射技术的原子分子动力学研究

The technique of X-ray scattering is a powerful tool to study the structures of atoms and molecules, and its unique advantage is that it can be used to reveal the comprehensive information of wave function distribution in momentum space of ground state and excited states of atom, molecule, and materials. Therefore, almost all of the third generation synchrotron radiation facilities in the world equipped the X-ray scattering spectrometer such as Compton scattering spectrometer as well as angle-resolved elastic or inelastic X-ray scattering spectrometer, and the X-ray scattering, especially the inelastic X-ray scattering, is an important research direction in the third generation synchrotron radiation. However, these techniques are absent in Shanghai light source. Therefore, this project plan to design and build Compton scattering spectrometer, angle-resolved elastic and inelastic X-ray scattering spectrometer in BL15U1 beamline station in Shanghai light source, and the BL15U1 station can be extended to study the dynamic parameters of atoms, molecules and materials. Then we will measure Compton profiles, the differential cross sections, as well as the squared form factors of elastic and inelastic scattering of He, Ne, Ar, O2, H2O, and CO2, and the momentum transfer dependence behavior of the dynamic parameters of ground and excited states of these atoms and molecules can be elucidated from different viewpoints. This project will not only extend the application area of BL15U1 beamline station, but also give the comprehensive information of the wave function distributions in the momentum space of the ground and excited states of He, Ne, Ar, O2, H2O, and CO2.

X射线散射技术是探测原子分子结构的强有力工具，它的独特优势是可以揭示原子分子和材料的波函数在动量空间的分布信息。因此，国际上第三代同步辐射几乎都装备有康普顿散射谱仪、角分辨的弹性和非弹性X射线散射谱仪，且这些X射线散射技术已经是第三代同步辐射的重要应用方向，而这恰恰是上海光源目前所缺失的实验技术。因此，本项目拟在上海光源BL15U1线站上设计并建造康普顿散射谱仪、角分辨的弹性和非弹性X射线散射谱仪，拓宽BL15U1线站的应用范围至原子、分子和材料的动力学参数研究。在发展装置的基础上，精确测量He、Ne、Ar、O2、H2O、CO2等原子分子的康普顿轮廓、弹性和非弹性的微分散射截面和形状因子平方，从不同的侧面揭示这些原子分子动力学参数的动量转移依赖特性。本项目工作的开展，一方面将大大拓宽BL15U1线站的应用范围，另一方面将给出上述原子分子完整的、从基态到激发态的波函数在动量空间中的分布信息。

在上海光源的BL15U1线站上建成了康普顿散射谱仪和非弹性X射线散射谱仪。前者的能量分辨在10keV时达到了220eV，相应动量分辨1.5a.u.。后者是国内首台非弹性X射线散射谱仪，在9.9keV入射光子能量时能量分辨达到了1.3eV，实现转角范围0°-120°，转角精度好于0.1°。作为国内第一台也是唯一的一台非弹性X射线散射谱仪，其建成极大地拓宽了BL15U1的应用范围，为国内同行开展原子、分子和材料的动力学行为研究创造了条件。.基于非弹性X射线散射技术，提出、实现并命名了测量原子分子光吸收截面的dipole（r,r)方法，该方法可以克服常规光吸收方法存在线饱和效应的不足和dipole (e, e)方法中Bethe-Born因子剧烈变化的影响，目前看来是唯一一种可以批量获得原子分子分立跃迁精确光学振子强度的实验方法。.在研制实验设备和发展实验方法的基础上，精确了测量He、Ar、N2、CO、CO2等原子分子的高精度康普顿轮廓、光学和广义振子强度、微分散射截面、积分截面的基准动力学参数，得到了这些原子分子基态和激发态的电子密度在动量空间及特定方向上的分布，揭示了原子分子中的电子关联效应及激发机制，进而为建立基本的物理图像提供了直接的实验依据，并为相关理论提供直接的实验基准。.相关工作已经发表基金资助SCI论文28篇，其中SCI论文25篇（含1区3篇）。