Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan.
Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, Notkestrasse 85, 22607 Hamburg, Germany.
Phys Rev Lett. 2018 Jun 1;120(22):223201. doi: 10.1103/PhysRevLett.120.223201.
We show that electron and ion spectroscopy reveals the details of the oligomer formation in Ar clusters exposed to an x-ray free electron laser (XFEL) pulse, i.e., chemical dynamics triggered by x rays. With guidance from a dedicated molecular dynamics simulation tool, we find that van der Waals bonding, the oligomer formation mechanism, and charge transfer among the cluster constituents significantly affect ionization dynamics induced by an XFEL pulse of moderate fluence. Our results clearly demonstrate that XFEL pulses can be used not only to "damage and destroy" molecular assemblies but also to modify and transform their molecular structure. The accuracy of the predictions obtained makes it possible to apply the cluster spectroscopy, in connection with the respective simulations, for estimation of the XFEL pulse fluence in the fluence regime below single-atom multiple-photon absorption, which is hardly accessible with other diagnostic tools.
我们表明，电子和离子光谱揭示了在暴露于 X 射线自由电子激光（XFEL）脉冲的氩原子团簇中低聚物形成的细节，即 X 射线引发的化学动力学。在专用分子动力学模拟工具的指导下，我们发现范德华键、低聚物形成机制以及在团簇成分之间的电荷转移，都会显著影响由中等强度 XFEL 脉冲引发的离化动力学。我们的结果清楚地表明，XFEL 脉冲不仅可以用于“破坏和摧毁”分子组装体，还可以用于修饰和改变它们的分子结构。所获得的预测的准确性使得可以将簇光谱与相应的模拟结合起来，用于在单原子多光子吸收以下的强度范围内估计 XFEL 脉冲的强度，这是其他诊断工具难以实现的。
