激光场-库伦场双势耦合下的电子动力学特性的理论和实验研究

The coupling of laser fields and Coulumb potential has been shown critical in quantitatively understanding strong field phonomena and attosecond measurements, such as laser-induced tomography, diffraction imaging of molecules, and attosecond pulse characterization. Recent experiments have shown that Coulomb potential plays an important role in low energy spectra of above-threshold ionization photoelectron, and high harmonic generation. In addtion, the interference effects in laser-assisted attosecond photoionization of molecules requires exact determination of the phase shift in Coulomb scattering. Our recent theoretical and experimental study on Terahertz generation by two-color laser pulses demonstrates that laser-assisted forward scattering is crucial in the generation of THz photocurrents as well. However, so far it is still lack of systematic and through theretical investigation of those effects. Particularly the study on the correlation of THz and low energy photoelectron is absent. In this project, we are going to develop theoretical methods describing the electorn dynamics under Coulomb-laser coupling. Combining with experiments, we will study the role of Coulomb potential in THz generation, emission of low energy electrons and HHG, advancing the research on strong field and ultrafast physics.

库仑势和激光场的耦合对于定量理解强场现象和阿秒测量，例如激光诱导分子轨道层析成像，分子电子衍射成像，及阿秒脉冲的表征等等至关重要。近几年的实验进展表明阈值上电离产生的电子的低能谱峰，以及高次谐波的偏振状态与库仑势在激光场协同下的散射密切相关。在激光协同下的分子体系的阿秒光电离过程的干涉效应的分析也需要精确获取库仑势所导致的散射相移。特别是我们最近的双色场产生太赫兹的实验研究和理论分析也表明激光协同下的电子被库仑势的前向散射对于太赫兹电流的形成非常重要。但目前为止对该问题的理论研究不够深入，缺乏系统的理论处理。虽然太赫兹和低能电子都对库仑势非常敏感，国际上对二者关联的研究尚未开展。本项目将对此问题进行研究,发展激光协同库仑散射理论，结合实验对库仑势和激光场耦合下的电子动力学进行诊断，深入理解库仑势在太赫兹辐射、低能电子发射和高次谐波辐射等强场物理现象中扮演的角色，推动强场和超快物理发展。

本项目研究库仑势和激光场的耦合下电子动力学产生的丰富物理现象（太赫兹辐射、阈值上电离电子低能、里德堡态及高次谐波产生等）的内在关联，验证了项目组前期提出的双色场产生太赫兹源于激光协同下的电子被库仑势的前向散射产生的光电流理论，观测到了圆偏振双色场对太赫兹辐射增强。自主研发强场物理计算模型以及第一原理含时多体计算程序，推动了强场物理模型计算的发展，为揭示实验结果背后的物理机制提供了有力工具。进一步完善了项目组独创的太赫兹与高次谐波一维和二维同步探测技术（HATS，2D-HATS），实现了分子电离微分截面的全光单次准确测量和对分子不同轨道参与相干辐射的精确操控，发表论文24篇（包括PRL1篇）， 获湖南省自然科学一等奖1项。项目组还初步探索了固体结构产生高次谐波机制，为探测固体周期性结构和电子微观动力学奠定基础。项目组培养人才质量较高，1人获学校优秀博士论文，1人获全军优秀博士论文。参与国际国内学术交流40余次，成果得到国际公认，取得良好的学术交流成效。