Kobayashi Yuki, Zeng Tao, Neumark Daniel M, Leone Stephen R
Department of Chemistry, University of California, Berkeley, California 94720, USA.
Department of Chemistry, Carleton University, Ottawa, Ontario K1S5B6, Canada.
Struct Dyn. 2019 Jan 30;6(1):014101. doi: 10.1063/1.5085011. eCollection 2019 Jan.
Ultrafast X-ray/XUV transient absorption spectroscopy is a powerful tool for real-time probing of chemical dynamics. Interpretation of the transient absorption spectra requires knowledge of core-excited potentials, which necessitates assistance from high-level electronic-structure computations. In this study, we investigate Br-3 core-excited electronic structures of hydrogen bromide (HBr) using spin-orbit general multiconfigurational quasidegenerate perturbation theory (SO-GMC-QDPT). Potential energy curves and transition dipole moments are calculated from the Franck-Condon region to the asymptotic limit and used to construct core-to-valence absorption strengths for five electronic states of HBr ( ) and two electronic states of HBr (Π, Σ). The results illustrate the capabilities of Br-3 edge probing to capture transitions of the electronic-state symmetry as well as nonadiabatic dissociation processes that evolve across avoided crossings. Furthermore, core-to-valence absorption spectra are simulated from the neutral state and the ionic states by numerically solving the time-dependent Schrödinger equation and exhibit excellent agreement with the experimental spectrum. The comprehensive and quantitative picture of the core-excited states obtained in this work allows for transparent analysis of the core-to-valence absorption signals, filling gaps in the theoretical understanding of the Br-3 transient absorption spectra.
超快X射线/极紫外瞬态吸收光谱是实时探测化学动力学的有力工具。对瞬态吸收光谱的解释需要了解芯激发势，这需要高水平电子结构计算的辅助。在本研究中，我们使用自旋轨道广义多组态准简并微扰理论（SO-GMC-QDPT）研究了溴化氢（HBr）的Br-3芯激发电子结构。计算了从弗兰克-康登区域到渐近极限的势能曲线和跃迁偶极矩，并用于构建HBr的五个电子态（ ）和HBr的两个电子态（Π，Σ）的芯到价吸收强度。结果说明了Br-3边探测捕获电子态对称性跃迁以及在避免交叉处演化的非绝热解离过程的能力。此外，通过数值求解含时薛定谔方程，从中性 态和离子 态模拟了芯到价吸收光谱，与实验光谱显示出极好的一致性。这项工作中获得的芯激发态的全面定量图景允许对芯到价吸收信号进行透明分析，填补了对Br-（3）瞬态吸收光谱理论理解的空白。
