Attosecond extreme ultraviolet (XUV) and soft x-ray sources provide powerful new tools for studying ultrafast molecular dynamics with atomic, state, and charge specificity. In this report, we employ attosecond transient absorption spectroscopy (ATAS) to follow strong-field-initiated dynamics in vinyl bromide. Probing the Br M edge allows one to assess the competing processes in neutral and ionized molecular species. Using ab initio non-adiabatic molecular dynamics, we simulate the neutral and cationic dynamics resulting from the interaction of the molecule with the strong field. Based on the dynamics results, the corresponding time-dependent XUV transient absorption spectra are calculated by applying high-level multi-reference methods. The state-resolved analysis obtained through the simulated dynamics and related spectral contributions enables a detailed and quantitative comparison with the experimental data. The main outcome of the interaction with the strong field is unambiguously the population of the first three cationic states, D₁, D₂, and D₃. The first two show exclusively vibrational dynamics while the D₃ state is characterized by an ultrafast dissociation of the molecule via C–Br bond rupture within 100 fs in 50% of the analyzed trajectories. The combination of the three simulated ionic transient absorption spectra is in excellent agreement with the experimental results. This work establishes ATAS in combination with high-level multi-reference simulations as a spectroscopic technique capable of resolving coupled non-adiabatic electronic-nuclear dynamics in photoexcited molecules with sub-femtosecond resolution.

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溴乙烯的超快强场离解：阿秒瞬态吸收光谱和非绝热分子动力学研究

阿秒极紫外 (XUV) 和软 X 射线源为研究具有原子、状态和电荷特异性的超快分子动力学提供了强大的新工具。在本报告中，我们采用阿秒瞬态吸收光谱 (ATAS) 来跟踪溴乙烯中的强场引发动力学。探测 Br M 边缘可以评估中性和电离分子物种中的竞争过程。从头开始使用非绝热分子动力学，我们模拟由分子与强场相互作用产生的中性和阳离子动力学。基于动力学结果，通过应用高级多参考方法计算相应的时间相关的 XUV 瞬态吸收光谱。通过模拟动力学和相关光谱贡献获得的状态分辨分析能够与实验数据进行详细和定量的比较。与强场相互作用的主要结果是前三个阳离子状态D ₁、D ₂和D _{3 的数量}。前两个仅显示振动动力学，而D ₃状态的特征在于分子通过 C-Br 键断裂在 100 fs 内以 50% 的分析轨迹发生超快解离。三个模拟离子瞬态吸收光谱的组合与实验结果非常吻合。这项工作将 ATAS 与高级多参考模拟相结合，作为一种光谱技术，能够以亚飞秒分辨率解析光激发分子中的耦合非绝热电子核动力学。