场致重散射光电子动量分布与电子-分子离子散射微分截面获取

Conventional electron diffraction is an important method for establishing the structure of the molecule, but this method currently cannot probe the inner molecular femtosecond time-resolved dynamics. This project is aiming to explore and develop a new electron diffraction method, which based on the electron self-imaging mechanism during the interaction between molecule and intense laser field, for researching the ultrafast molecular structural variation. This method is founded on the three-step rescattering model, and its central important question is extracting the electron-molecular ion elastic differential scattering cross sections. In this project, we will experimentally measure the laser-induced rescattering electron spectroscopy of molecules, and control the returning electron wavepacket by adjusting the parameters of the ultrafast laser pulses, then basing on the typical photoelectron momentum distributions in those situations,we will explore that how the mechanism of tunneling ionization of the first step, such as multiorbital interference, affects electron-ion scattering process of the third step in the three-step rescattering model, then combine those researches and the quantitative rescattering theory, we may extract the electron-ion elastic differential scattering cross sections.

常规电子衍射是探测分子结构的重要方法,但此方法无法实现超快时间分辨的分子内部动力学过程研究。本项目旨在探索发展一种基于强激光场中分子隧穿电离的电子返回母体离子散射而形成"自成像"获取分子结构超快变化的新的电子衍射方法。这一方法基于电子重散射三步模型，其核心物理问题是从重散射电子中提取电子-分子离子弹性散射的微分散射截面。项目拟实验测量一系列分子的激光场致重散射光电子动量谱，实现通过超快光场调控作为散射电子束源的返回电子波包，进而根据不同条件下重散射光电子动量分布的变化规律，探讨三步电子重散射模型中第一步的隧穿电离机制对第三步电子-离子弹性散射的影响，特别是多轨道干涉效应等的影响，并在此基础上结合定量重散射理论，获取电子-分子离子弹性散射的微分散射截面。

本项目旨在探索发展一种基于强激光场中分子隧穿电离的电子返回母体离子散射而形成“自成相”来获取分子结构变化的新电子衍射方法—激光场致电子衍射。我们从该方法的核心物理问题-电子分子离子弹性散射的微分散射截面提取入手，提取了一系列典型多原子分子的微分散射截面，首次发现了内层占据轨道（HOMO-1）的隧穿电离对高能重散射电子的影响，同时证明多原子分子的不同中心对其有不同贡献；我们还进一步的应用中红外激光拓展了返回电子能量，在获得的苯分子的电子-分子离子的微分散射截面的基础上，首次实现了应用激光场致电子衍射方法提取环状分子苯的C-C键和C-H键的键长。我们的研究证明了在超快强激光实验室即可实现对分子内的原子位置进行埃量级上超快成像，同时我们从机制上完善了激光场致电子衍射方法，对其未来的进一步应用具有重要意义。