Kuraoka T, Goto S, Kanno M, Díaz-Tendero S, Reino-González J, Trinter F, Pier A, Sommerlad L, Melzer N, McGinnis O D, Kruse J, Wenzel T, Jahnke T, Xue H, Kishimoto N, Yoshikawa K, Tamura Y, Ota F, Hatada K, Ueda K, Martín F
Department of Physics, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan.
Department of Chemistry, Tohoku University, 6-3 Aramaki Aza-Aoba, Aoba-ku, Sendai 980-8578, Japan.
J Phys Chem A. 2024 Feb 22;128(7):1241-1249. doi: 10.1021/acs.jpca.3c07640. Epub 2024 Feb 7.
The recent implementation of attosecond and few-femtosecond X-ray pump/X-ray probe schemes in large-scale free-electron laser facilities has opened the way to visualize fast nuclear dynamics in molecules with unprecedented temporal and spatial resolution. Here, we present the results of theoretical calculations showing how polarization-averaged molecular-frame photoelectron angular distributions (PA-MFPADs) can be used to visualize the dynamics of hydrogen migration in methanol, ethanol, propanol, and isopropyl alcohol dications generated by X-ray irradiation of the corresponding neutral species. We show that changes in the PA-MFPADs with the pump-probe delay as a result of intramolecular photoelectron diffraction carry information on the dynamics of hydrogen migration in real space. Although visualization of this dynamics is more straightforward in the smaller systems, methanol and ethanol, one can still recognize the signature of that motion in propanol and isopropyl alcohol and assign a tentative path to it. A possible pathway for a corresponding experiment requires an angularly resolved detection of photoelectrons in coincidence with molecular fragment ions used to define a molecular frame of reference. Such studies have become, in principle, possible since the first XFELs with sufficiently high repetition rates have emerged. To further support our findings, we provide experimental evidence of H migration in ethanol-OD from ion-ion coincidence measurements performed with synchrotron radiation.
近期在大型自由电子激光设施中实现的阿秒和飞秒级X射线泵浦/X射线探测方案，为以前所未有的时间和空间分辨率可视化分子中的快速核动力学开辟了道路。在此，我们展示了理论计算结果，表明极化平均分子框架光电子角分布（PA-MFPADs）可如何用于可视化由相应中性物种的X射线辐照产生的甲醇、乙醇、丙醇和异丙醇二价阳离子中氢迁移的动力学。我们表明，由于分子内光电子衍射导致的PA-MFPADs随泵浦-探测延迟的变化携带了真实空间中氢迁移动力学的信息。尽管在较小的系统甲醇和乙醇中这种动力学的可视化更直接，但在丙醇和异丙醇中仍能识别出该运动的特征并为其确定一条暂定路径。相应实验的一条可能途径需要与用于定义分子参考框架的分子碎片离子符合探测光电子的角度分辨。自从出现了具有足够高重复率的首批X射线自由电子激光以来，此类研究原则上已成为可能。为了进一步支持我们的发现，我们提供了通过同步辐射进行的离子-离子符合测量得出的乙醇-OD中氢迁移的实验证据。
