Generation, Characterization and Application of Chiral Attosecond Pulses

高次谐波产生是桌面上明亮的相干极端紫外线和软X射线脉冲的使能技术，其持续时间为阿秒(1As=10E−18s)时间尺度，即物质中电子响应的时间尺度。这一建议解决了这种脉冲的产生、表征和应用中的关键方面：对其偏振特性的灵活控制。从手性分子中的螺旋电荷流到具有桌面设置的超快磁光光谱学，圆偏振阿秒脉冲的可用性对于跟踪超快电子动力学是必不可少的。我们的联合理论和实验项目将开发和展示新的方案，用于i)产生孤立的和连续的手性阿秒脉冲，ii)完全表征它们的偏振状态，包括螺旋度随时间变化几十的脉冲，以及ii)使用它们在电子时间尺度上对分子中的手征电荷流动进行成像实验。我们还将使用频率上转换过程，即高次谐波产生，来可视化自旋-轨道相互作用如何旋转原子离子价层中的自旋和角动量，并在时间上解决强光场从原子中重新俘获的电子进入高度激发但稳定的轨道。

High harmonic generation is the enabling technology for table-top sources of bright coherent extreme ultraviolet and soft x-ray pulses with durations on attosecond (1 as = 10E−18s) time-scale, the time-scale of electronic response in matter. This proposal addresses the key aspect in  generation, characterization, and application of such pulses: flexible control over their polarization properties.  Availability of circularly polarized attosecond pulses would be indispensable for tracking ultrafast electronic dynamics, from helical charge flows in chiral molecules to ultrafast magneto-optical spectroscopy, with table-top setup. Our joint theoretical and experimental project will develop and demonstrate new schemes for i) generating chiral attosecond pulses, isolated and trains, ii) fully characterizing their polarization state, including pulses where helicity changes on few ten as time-scale, and ii) use them to perform experiments on imaging chiral charge flow in molecules on the electronic time-scale. We will also use the frequency up-conversion process, the high harmonic generation, to visualize how spin-orbit interaction rotates the spin and angular momentum in valence shells of atomic ions, and to time resolve the recapture of electrons, liberated from atoms by intense light fields, into highly excited but stable orbits.