High-harmonic spectroscopy is an all-optical technique with inherent attosecond temporal resolution that has been successfully employed to reconstruct charge migration, electron-tunneling dynamics, and conical-intersection dynamics. Here, we demonstrate the extension of two key components of high-harmonic spectroscopy, i.e., impulsive alignment and measurements with multiple driving wavelengths to 1,3-cyclohexadiene and benzene. In the case of 1,3-cyclohexadiene, we find that the temporal sequence of maximal and minimal emitted high-harmonic intensities as a function of the delay between the alignment and probe pulses inverts between 25 and 30 eV and again between 35 and 40 eV when an 800-nm driver is used, but no inversions are observed with a 1420-nm driver. This observation is explained by the wavelength-dependent interference of emission from multiple molecular orbitals (HOMO to HOMO-3), as demonstrated by calculations based on the weak-field asymptotic theory and accurate photorecombination matrix elements. These results indicate that attosecond charge migration takes place in the 1,3-cyclohexadiene cation and can potentially be reconstructed with the help of additional measurements. Our experiments also demonstrate a pathway toward studying photochemical reactions in the molecular frame of 1,3-cyclohexadiene.

中文翻译：

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脉冲排列 1,3-环己二烯的高次谐波光谱：阿秒电荷迁移特征

高次谐波光谱是一种具有固有阿秒时间分辨率的全光学技术，已成功用于重建电荷迁移、电子隧道动力学和圆锥相交动力学。在这里，我们展示了高次谐波光谱的两个关键组成部分的扩展，即脉冲对准和多驱动波长测量对 1,3-环己二烯和苯的影响。对于 1,3-环己二烯，我们发现最大和最小发射高次谐波强度的时间序列作为对准脉冲和探测脉冲之间的延迟的函数在 25 和 30 eV 之间反转，并再次在 35 和 40 eV 之间反转当使用 800 nm 驱动器时，但使用 1420 nm 驱动器时未观察到反转。这一观察结果可以通过多个分子轨道（HOMO 到 HOMO-3）发射的波长相关干涉来解释，基于弱场渐近理论和精确光复合矩阵元素的计算证明了这一点。这些结果表明阿秒电荷迁移发生在 1,3-环己二烯阳离子中，并且可以借助额外的测量来重建。我们的实验还展示了研究 1,3-环己二烯分子框架中光化学反应的途径。