该研究团队从理论上提出了一种多维高谐波回波光谱技术，并利用强光场来解析跨越多个电子伏特能量范围的相干电子动力学。研究人员利用最近开发的半微扰方法，可以描述由一系列相位匹配且分离良好的短短少周期强红外激光脉冲驱动的相干价电子动力学。每个脉冲的隧道电离电子的复合相干地填充了分子的价态，这允许通过高谐波回波信号直接观察其动力学。
由强场激发产生的价态之间的有效偶极子的宽带宽导致了非平凡的超延迟部分重新定相回波，这在标准的二维光谱技术中是无法在两能级分子体系中观察到的。这项研究展示了阴离子分子体系的模拟结果，并表明可以用飞秒分辨率很好地捕获超快价电子动力学。
附：英文原文
Title: Multidimensional high-harmonic echo spectroscopy: Resolving coherent electron dynamics in the EUV regime
Author: Jiang, Shicheng, Gudem, Mahesh, Kowalewski, Markus, Dorfman, Konstantin
Issue&Volume: 2024-2-5
Abstract: We theoretically propose a multidimensional high-harmonic echo spectroscopy technique which utilizes strong optical fields to resolve coherent electron dynamics spanning an energy range of multiple electronvolts. Using our recently developed semi-perturbative approach, we can describe the coherent valence electron dynamics driven by a sequence of phase-matched and well-separated short few-cycle strong infrared laser pulses. The recombination of tunnel-ionized electrons by each pulse coherently populates the valence states of a molecule, which allows for a direct observation of its dynamics via the high harmonic echo signal. The broad bandwidth of the effective dipole between valence states originated from the strong-field excitation results in nontrivial ultra-delayed partial rephasing echo, which is not observed in standard two-dimensional optical spectroscopic techniques in a two-level molecular systems. We demonstrate the results of simulations for the anionic molecular system and show that the ultrafast valence electron dynamics can be well captured with femtosecond resolution.
DOI: 10.1073/pnas.2304821121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2304821121