Bäuml Lena, Rott Florian, Schnappinger Thomas, de Vivie-Riedle Regina
Department of Chemistry, LMU Munich, Munich 81377, Germany.
J Phys Chem A. 2023 Nov 23;127(46):9787-9796. doi: 10.1021/acs.jpca.3c06509. Epub 2023 Nov 13.
The nucleobase uracil exhibits high photostability due to ultrafast relaxation processes mediated by conical intersections (CoIns), where the interplay between nuclear and electron dynamics becomes crucial. In our previous study, we observed seemingly long-lived traces of electronic coherence for the relaxation process through the / CoIn by applying our ansatz for coupled nuclear and electron dynamics in molecules (NEMol). In this work, we theoretically investigate how time-dependent transient X-ray absorption spectroscopy can be used to observe this ultrafast dynamics. Therefore, we calculated X-ray absorption spectra (XAS) for the oxygen K-edge, using a multireference protocol in combination with NEMol dynamics. Thus, we have access to both the transient XAS based on the nuclear wavepacket dynamics and the modulation of the signals caused by the electronic coherence induced by the excitation process and the presence of a CoIn seam. In both cases, we were able to qualitatively predict its influence on the resulting XAS.
核碱基尿嘧啶由于由锥形交叉点（CoIns）介导的超快弛豫过程而表现出高光稳定性，其中核动力学和电子动力学之间的相互作用变得至关重要。在我们之前的研究中，通过应用我们的分子中核与电子动力学耦合的假设（NEMol），我们观察到了通过/CoIn进行弛豫过程时看似长寿命的电子相干痕迹。在这项工作中，我们从理论上研究了如何利用随时间变化的瞬态X射线吸收光谱来观察这种超快动力学。因此，我们使用多参考协议结合NEMol动力学计算了氧K边的X射线吸收光谱（XAS）。这样，我们既可以获得基于核波包动力学的瞬态XAS，也可以获得由激发过程和CoIn缝的存在所诱导的电子相干引起的信号调制。在这两种情况下，我们都能够定性地预测其对所得XAS的影响。
