Generation, Characterization and Application of Chiral Attosecond Pulses

高次谐波产生是使桌面光源能够产生明亮的相干极紫外和软X射线脉冲的技术，其持续时间为阿秒（1 as = 10 E − 18 s）时间尺度，即物质中电子响应的时间尺度。该建议解决了产生，表征和应用这些脉冲的关键方面：灵活控制其偏振特性。 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，从手性分子中的螺旋电荷流到超快磁光光谱，具有桌面设置。我们的联合理论和实验项目将开发和展示新的方案，i）产生手性阿秒脉冲，隔离和列车，ii）充分表征其偏振状态，包括螺旋度在几十个时间尺度上变化的脉冲，ii）使用它们来进行实验，在电子时间尺度上成像分子中的手性电荷流。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，并时间分辨电子的重新捕获，通过强光场从原子中释放，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.