Visualizing conical intersection passages via vibronic coherence maps generated by stimulated ultrafast X-ray Raman signals
Visualizing conical intersection passages via vibronic coherence maps generated by stimulated ultrafast X-ray Raman signals
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DOI：
10.1073/pnas.2015988117
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发表时间：
2020-09-29
影响因子：
11.1
通讯作者：
Mukamel, Shaul
中科院分区：
文献类型：
--
作者：
Keefer, Daniel;Schnappinger, Thomas;Mukamel, Shaul
事实上，所有的光物理和光化学过程的速率和结果都是由圆锥相交决定的。这些是分子的核景观上的电子状态之间的简并区域，其中电子和原子核在可比的时间尺度上演化，因此变得强耦合，从而在光激发时实现无辐射弛豫通道。由于其超快的性质和巨大的复杂性，监测圆锥路口实验是一个开放的挑战。基于原子核的量子描述，我们对尿嘧啶的超快光弛豫进行了模拟研究。我们证明了一个额外的窗口，通过记录瞬态波包的相干性，在此期间与X射线自由电子激光脉冲通过锥形交叉点。报告了两项主要的调查结果。首先，我们发现，在圆锥形交叉点的振动相干性的生活几百飞秒，可以在这整个时间测量。第二，直接从信号的维格纳谱图中提取参与振动和电子态的随时间变化的能量分裂景观。这些提供了一个物理图像的量子圆锥交叉路径，通过可视化其瞬态振动相干分布。核波包在圆锥形交叉点附近的路径直接映射的建议的实验。
The rates and outcomes of virtually all photophysical and photochemical processes are determined by conical intersections. These are regions of degeneracy between electronic states on the nuclear landscape of molecules where electrons and nuclei evolve on comparable timescales and thus become strongly coupled, enabling radiationless relaxation channels upon optical excitation. Due to their ultrafast nature and vast complexity, monitoring conical intersections experimentally is an open challenge. We present a simulation study on the ultrafast photorelaxation of uracil, based on a quantum description of the nuclei. We demonstrate an additional window into conical intersections obtained by recording the transient wavepacket coherence during this passage with an X-ray free-electron laser pulse. Two major findings are reported. First, we find that the vibronic coherence at the conical intersection lives for several hundred femtoseconds and can be measured during this entire time. Second, the time-dependent energy-splitting landscape of the participating vibrational and electronic states is directly extracted from Wigner spectrograms of the signal. These offer a physical picture of the quantum conical intersection pathways through visualizing their transient vibronic coherence distributions. The path of a nuclear wavepacket in the vicinity of the conical intersection is directly mapped by the proposed experiment.